Add GitHub CI

.github/workflows/android.yml

@@ -0,0 +1,24 @@
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v2
+    - name: set up JDK 11
+      uses: actions/setup-java@v2
+      with:
+        java-version: '11'
+        distribution: 'adopt'
+        cache: gradle
+
+    - name: Grant execute permission for gradlew
+      run: chmod +x gradlew
+    - name: Build with Gradle
+      run: ./gradlew build
+    - name: Upload Debug APK
+      uses: actions/upload-artifact@v2
+        if: ${{ !github.head_ref }}
+        with:
+          name: apk-debug
+          path: app/build/outputs/apk/debug