Add build APK action to CI

.github/workflows/android.yml

@@ -0,0 +1,22 @@
+name: Android CI
+on:
+  push:
+    branches:
+      - master
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout Repo
+        uses: actions/checkout@v2
+      - name: set up JDK 1.8
+        uses: actions/setup-java@v1
+        with:
+          java-version: 1.8
+      - name: Set Gradle as executable
+        run: chmod +x ./gradlew
+      - name: Build with Gradle
+        run: ./gradlew build
+      - name: Build Debug APK
+        run: ./gradlew assembleDebug