Better navbar styling and external project links

Currently, the navbar lacks styling, and only provides links to the home and explorer pages.
This change adds:
* Better styling for the navbar
* External links to SourceCred github and twitter
Test plan: visual inspection

src/app/GithubLogo.js

@@ -0,0 +1,22 @@
+// @flow
+import React from "react";
+
+type Props = {|
+  +className: string,
+  +altText: string,
+|};
+
+export default function GithubLogo(props: Props) {
+  return (
+    <svg
+      aria-label={props.altText}
+      role="img"
+      className={props.className}
+      viewBox="0 0 1024 1024"
+      xmlns="http://www.w3.org/2000/svg"
+    >
+      <title>{props.altText}</title>
+      <path d="M512 0C229.25 0 0 229.25 0 512c0 226.25 146.688 418.125 350.156 485.812 25.594 4.688 34.938-11.125 34.938-24.625 0-12.188-0.469-52.562-0.719-95.312C242 908.812 211.906 817.5 211.906 817.5c-23.312-59.125-56.844-74.875-56.844-74.875-46.531-31.75 3.53-31.125 3.53-31.125 51.406 3.562 78.47 52.75 78.47 52.75 45.688 78.25 119.875 55.625 149 42.5 4.654-33 17.904-55.625 32.5-68.375C304.906 725.438 185.344 681.5 185.344 485.312c0-55.938 19.969-101.562 52.656-137.406-5.219-13-22.844-65.094 5.062-135.562 0 0 42.938-13.75 140.812 52.5 40.812-11.406 84.594-17.031 128.125-17.219 43.5 0.188 87.312 5.875 128.188 17.281 97.688-66.312 140.688-52.5 140.688-52.5 28 70.531 10.375 122.562 5.125 135.5 32.812 35.844 52.625 81.469 52.625 137.406 0 196.688-119.75 240-233.812 252.688 18.438 15.875 34.75 47 34.75 94.75 0 68.438-0.688 123.625-0.688 140.5 0 13.625 9.312 29.562 35.25 24.562C877.438 930 1024 738.125 1024 512 1024 229.25 794.75 0 512 0z" />
+    </svg>
+  );
+}

src/app/Page.js

@@ -2,7 +2,9 @@
 
 import React, {type Node} from "react";
 import {Link} from "react-router";
-
+import {StyleSheet, css} from "aphrodite/no-important";
+import GithubLogo from "./GithubLogo";
+import TwitterLogo from "./TwitterLogo";
 import {routeData} from "./routeData";
 import * as NullUtil from "../util/null";
 
@@ -11,15 +13,47 @@ export default class Page extends React.Component<{|+children: Node|}> {
     return (
       <div>
         <header>
-          <nav>
+          <nav className={css(style.nav)}>
-            <ul style={{listStyle: "none", paddingLeft: 0, margin: 0}}>
+            <ul className={css(style.navList)}>
+              <li className={css(style.navItem, style.navItemLeft)}>
+                <Link to="/" className={css(style.navLinkTitle, style.navLink)}>
+                  SourceCred
+                </Link>
+              </li>
               {routeData.map(({navTitle, path}) =>
                 NullUtil.map(navTitle, (navTitle) => (
-                  <li key={path} style={{display: "inline", marginRight: 10}}>
+                  <li
-                    <Link to={path}>{navTitle}</Link>
+                    key={path}
+                    className={css(style.navItem, style.navItemRight)}
+                  >
+                    <Link to={path} className={css(style.navLink)}>
+                      {navTitle}
+                    </Link>
                   </li>
                 ))
               )}
+              <li className={css(style.navItem, style.navItemRight)}>
+                <a
+                  className={css(style.navLink)}
+                  href="https://github.com/sourcecred/sourcecred"
+                >
+                  <GithubLogo
+                    altText="SourceCred Github"
+                    className={css(style.navLogo)}
+                  />
+                </a>
+              </li>
+              <li className={css(style.navItem, style.navItemRight)}>
+                <a
+                  className={css(style.navLink)}
+                  href="https://twitter.com/sourcecred"
+                >
+                  <TwitterLogo
+                    altText="SourceCred Twitter"
+                    className={css(style.navLogo)}
+                  />
+                </a>
+              </li>
             </ul>
           </nav>
         </header>
@@ -28,3 +62,41 @@ export default class Page extends React.Component<{|+children: Node|}> {
     );
   }
 }
+
+const style = StyleSheet.create({
+  nav: {
+    height: 60,
+    padding: "20px 100px",
+  },
+  navItem: {
+    display: "inline-block",
+  },
+  navList: {
+    listStyle: "none",
+    paddingLeft: 0,
+    margin: 0,
+    display: "flex",
+  },
+  navLink: {
+    color: "#0872A2",
+    fill: "#0872A2",
+    fontFamily: "Roboto Condensed",
+    fontSize: 18,
+    textDecoration: "none",
+    ":hover": {
+      color: "#084598",
+      fill: "#084598",
+      textDecoration: "underline",
+    },
+  },
+  navItemLeft: {
+    flex: 1,
+  },
+  navItemRight: {
+    marginLeft: 20,
+  },
+  navLogo: {
+    height: 20,
+    width: 20,
+  },
+});

src/app/TwitterLogo.js

@@ -0,0 +1,34 @@
+// @flow
+import React from "react";
+
+type Props = {|
+  +className: string,
+  +altText: string,
+|};
+
+export default function TwitterLogo(props: Props) {
+  return (
+    <svg
+      aria-label={props.altText}
+      role="img"
+      className={props.className}
+      version="1.1"
+      xmlns="http://www.w3.org/2000/svg"
+      x="0px"
+      y="0px"
+      viewBox="0 0 512 512"
+    >
+      <title>{props.altText}</title>
+      <path
+        d="M512,97.209c-18.838,8.354-39.082,14.001-60.329,16.54c21.687-13,38.343-33.585,46.187-58.114
+      c-20.299,12.038-42.778,20.779-66.705,25.489c-19.16-20.415-46.461-33.17-76.674-33.17c-58.012,0-105.043,47.029-105.043,105.039
+      c0,8.233,0.929,16.25,2.72,23.939c-87.3-4.382-164.701-46.2-216.509-109.753c-9.042,15.514-14.224,33.558-14.224,52.809
+      c0,36.444,18.544,68.596,46.73,87.433c-17.219-0.546-33.416-5.271-47.577-13.139c-0.01,0.438-0.01,0.878-0.01,1.321
+      c0,50.894,36.209,93.348,84.261,103c-8.813,2.398-18.094,3.686-27.674,3.686c-6.77,0-13.349-0.66-19.764-1.887
+      c13.367,41.73,52.159,72.104,98.126,72.949c-35.95,28.175-81.243,44.967-130.458,44.967c-8.479,0-16.841-0.497-25.059-1.471
+      c46.486,29.806,101.701,47.197,161.021,47.197c193.211,0,298.868-160.063,298.868-298.873c0-4.554-0.104-9.084-0.305-13.59
+      C480.11,136.773,497.918,118.273,512,97.209z"
+      />
+    </svg>
+  );
+}

src/app/index.css

@@ -1,5 +1,5 @@
 body {
   margin: 0;
   padding: 0;
-  font-family: sans-serif;
+  font-family: 'Roboto', sans-serif;
 }

src/app/routeData.js

@@ -34,7 +34,7 @@ const routeData /*: $ReadOnlyArray<RouteDatum> */ = [
       component: () => require("./credExplorer/App").default,
     },
     title: "SourceCred explorer",
-    navTitle: "Explorer",
+    navTitle: "Explore",
   },
   {
     path: "/discord-invite",

src/app/server.js

@@ -43,6 +43,8 @@ export default function render(
           <meta charset="utf-8">
           <meta name="viewport" content="width=device-width,initial-scale=1" />
           <link rel="shortcut icon" href="/favicon.ico" />
+          <link href="https://fonts.googleapis.com/css?family=Roboto" rel="stylesheet">
+          <link href="https://fonts.googleapis.com/css?family=Roboto+Condensed" rel="stylesheet">
           <title>${resolveTitleFromPath(path)}</title>
           <style>${require("./index.css")}</style>
           <style data-aphrodite>${css.content}</style>
@@ -79,6 +81,8 @@ export default function render(
       <meta name="viewport" content="width=device-width,initial-scale=1" />
       <meta http-equiv="refresh" content="0;url=${redirectTo}" />
       <link rel="shortcut icon" href="/favicon.ico" />
+      <link href="https://fonts.googleapis.com/css?family=Roboto" rel="stylesheet">
+      <link href="https://fonts.googleapis.com/css?family=Roboto+Condensed" rel="stylesheet">
       <title>${resolveTitleFromPath(path)}</title>
       <style>${require("./index.css")}</style>
       <style data-aphrodite>${css.content}</style>