feat(ci): add a build action on push

.github/workflows/build.yml

@@ -0,0 +1,28 @@
+# This workflow will build a Java project with Gradle
+
+name: Build
+
+on: [push]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: Set up JDK 12
+        uses: actions/setup-java@v1
+        with:
+          java-version: 12
+      - name: Grant execute permission for gradlew
+        run: chmod +x gradlew
+      - name: Build
+        run: ./gradlew build
+      - name: Assemble
+        run: ./gradlew assembleDebug
+      - name: Upload APKs
+        uses: actions/upload-artifact@v3
+        with:
+          name: apks
+          path: |
+            app/**/build/outputs/apk/debug/*.apk
+