chore: deploy pull requests to expo

.github/workflows/expo-preview.yml

@@ -0,0 +1,49 @@
+name: Expo Preview
+on: [pull_request]
+
+jobs:
+  publish:
+    name: Install and publish
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v1
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v1
+        with:
+          node-version: 12.x
+
+      - name: Setup Expo
+        uses: expo/expo-github-action@v5
+        with:
+          expo-version: 3.x
+          expo-username: ${{ secrets.EXPO_CLI_USERNAME }}
+          expo-password: ${{ secrets.EXPO_CLI_PASSWORD }}
+          expo-cache: true
+
+      - name: Get yarn cache
+        id: yarn-cache
+        run: echo "::set-output name=dir::$(yarn cache dir)"
+
+      - name: Check yarn cache
+        uses: actions/cache@v1
+        with:
+          path: ${{ steps.yarn-cache.outputs.dir }}
+          key: ${{ runner.os }}-yarn-${{ hashFiles('**/yarn.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-yarn-
+
+      - name: Install dependencies
+        run: yarn
+
+      - name: Publish Expo app
+        working-directory: ./example
+        run: expo publish --release-channel=pr-${{ github.event.number }}
+
+      - name: Comment on PR
+        uses: unsplash/comment-on-pr@master
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        with:
+          msg: The Expo app for the example from this branch is ready!<br><br><a href="https://expo.io/@react-navigation/react-navigation-example?release-channel=pr-${{ github.event.number }}"><img src="https://api.qrserver.com/v1/create-qr-code/?size=200x200&data=exp://exp.host/@react-navigation/react-navigation-example?release-channel=pr-${{ github.event.number }}" height="200px" width="200px"></a>.

example/app.json

@@ -3,6 +3,7 @@
   "displayName": "React Navigation Example",
   "expo": {
     "name": "@react-navigation/example",
+    "owner": "react-navigation",
     "slug": "react-navigation-example",
     "description": "Demo app to showcase various functionality of React Navigation",
     "privacy": "public",