Add GitHub workflows

.github/workflows/android.yml

@@ -0,0 +1,28 @@
+name: Android CI
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
+
+jobs:
+  build:
+    name: Build and test
+    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 assembleDebug
+      - name: Run tests
+        run: ./gradlew test

.github/workflows/gradle-wrapper-validation.yml

@@ -0,0 +1,17 @@
+name: "Validate Gradle Wrapper"
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+    branches:
+      - main
+
+jobs:
+  validation:
+    name: "Validation"
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: gradle/wrapper-validation-action@v1