[Add] Github Action YAML file

- add backend for SongPlayer.mediaSession

.github/workflows/build.yml

@@ -0,0 +1,24 @@
+name: Build
+on:
+  push:
+    branches: [master]
+  pull_request:
+    branches: [master]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: Set up JDK 1.8
+        uses: actions/setup-java@v1
+        with:
+          java-version: 1.8
+      - name: Grant execute permission for gradlew
+        run: chmod +x gradlew
+      - name: Check Lint
+        run: sudo ./gradlew lintDebug
+      - name: Run tests
+        run: sudo ./gradlew test
+      - name: Build with Gradle
+        run: sudo ./gradlew build