create build workflow

.github/workflows/main.yml

@@ -0,0 +1,25 @@
+# This workflow will build a Java project with Gradle
+# For more information see: https://help.github.com/actions/language-and-framework-guides/building-and-testing-java-with-gradle
+
+name: Artifact Build
+
+on: [push, pull_request]
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v2
+    - name: Run Gradle command
+      uses: Raul6469/android-gradle-action@2.0.0
+      with:
+        # The gradle command you wish to run (required)
+        # Here, `./gradlew test` will be run
+        script: assembleDebug
+    - name: Upload Artifact
+      uses: actions/upload-artifact@v2
+      with:
+        name: pull-request-build
+        path: "*/*/build/outputs/apk/*.apk"