Add Google Play Publisher plugin and Play Store assets

.github/workflows/main.yml

@@ -1,6 +1,12 @@
 name: Build & Test
 
-on: [push]
+on:
+  push:
+    branches:
+      - dev
+  pull_request:
+    branches:
+      - dev
 
 jobs:
   build:

.github/workflows/publish.yml

@@ -0,0 +1,40 @@
+name: Build, Test & Publish
+
+on:
+  push:
+    branches:
+      - master
+
+jobs:
+  build:
+    runs-on: macOS-latest
+    steps:
+    - uses: actions/checkout@v1
+    - name: Install GPG
+      uses: olafurpg/setup-gpg@v2
+    - name: Decrypt secrets
+      env:
+        GPG_PASSWORD: ${{ secrets.GPG_PASSWORD }}
+      run: .secret/decrypt.sh
+    - name: Install Java Development Kit 1.8
+      uses: actions/setup-java@v1
+      with:
+        java-version: 1.8
+    - name: Build APK & Run small tests
+      env:
+        RELEASE: 1
+      run: android/build.sh build
+    - name: Run medium tests
+      uses: ReactiveCircus/android-emulator-runner@v2.2.0
+      env:
+        RELEASE: 1
+      with:
+        api-level: 29
+        script: android/build.sh medium-tests
+    - name: Upload build to GitHub
+      uses: actions/upload-artifact@v1
+      with:
+        name: Build
+        path: android/uhabits-android/build/outputs/
+    - name: Upload APK to Google Play
+      run: cd android && ./gradlew publishReleaseApk