install prettier and add config files

.prettierrc.json

@@ -0,0 +1,4 @@
+{
+  "singleQuote": true,
+  "trailingComma": "all"
+}

package-lock.json

@@ -2754,6 +2754,12 @@
       "integrity": "sha1-IZMqVJ9eUv/ZqCf1cOBL5iqX2lQ=",
       "dev": true
     },
+    "prettier": {
+      "version": "1.16.4",
+      "resolved": "https://registry.npmjs.org/prettier/-/prettier-1.16.4.tgz",
+      "integrity": "sha512-ZzWuos7TI5CKUeQAtFd6Zhm2s6EpAD/ZLApIhsF9pRvRtM1RFo61dM/4MSRUA0SuLugA/zgrZD8m0BaY46Og7g==",
+      "dev": true
+    },
     "process-nextick-args": {
       "version": "2.0.0",
       "resolved": "https://registry.npmjs.org/process-nextick-args/-/process-nextick-args-2.0.0.tgz",

package.json

@@ -5,6 +5,9 @@
   "main": "index.js",
   "scripts": {
     "coverage": "nyc --branches 100 --functions 100 --check-coverage npm run unit",
+    "format": "npm run prettier -- --write",
+    "format:ci": "npm run prettier -- --check",
+    "prettier": "prettier 'ts_src/**/*.ts' --ignore-path ./.prettierignore",
     "standard": "standard",
     "test": "npm run standard && npm run unit",
     "unit": "tape test/*.js",
@@ -33,6 +36,7 @@
   "devDependencies": {
     "node-fetch": "^1.6.3",
     "nyc": "^13.1.0",
+    "prettier": "^1.16.4",
     "proxyquire": "^1.7.10",
     "standard": "^10.0.2",
     "tape": "^4.6.2",