Add postinstall script to create symlinks

This includes a top-level "android" symlink that should allow `react-native link` command to work.

package.json

@@ -10,5 +10,8 @@
     "src",
     "vendor",
     "RealmJS.xcodeproj"
-  ]
+  ],
+  "scripts": {
+    "postinstall": "scripts/create-symlinks.sh"
+  }
 }

react-native/android/app/src/main/jni/.npmignore

@@ -0,0 +1 @@
+core/

scripts/create-symlinks.sh

@@ -0,0 +1,18 @@
+#!/bin/bash
+
+set -e
+set -o pipefail
+
+symlink() {
+  [ -e "$(basename "$1")" ] || ln -s "$1"
+}
+
+cd "$(dirname "$0")/.."
+
+# A top-level "android" directory is expected by `react-native link`
+symlink react-native/android
+
+# NPM doesn't support publishing symlinks, so these must be re-created
+cd react-native/android/app/src/main/jni
+symlink ../../../../../../src
+symlink ../../../../../../vendor