github: add github action tests

.github/workflows/android.yml

@@ -0,0 +1,24 @@
+name: Android CI
+
+on: [push, pull_request]
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/cache@v2
+        with:
+          path: ~/.gradle/caches
+          key: gradle-${{ runner.os }}-${{ hashFiles('**/build.gradle') }}-${{ hashFiles('**/gradle/wrapper/gradle-wrapper.properties') }}
+
+      - name: set up JDK 1.8
+        uses: actions/setup-java@v1
+        with:
+          java-version: 1.8
+      - name: Make gradlew executable
+        run: chmod +x ./gradlew
+      - name: Build with Gradle
+        run: ./gradlew build