CI: move to Github Actions

.github/workflows/gradle-check.yml

@@ -0,0 +1,19 @@
+name: Gralde check
+
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+    branches:
+      - master
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Clone repository
+        uses: actions/checkout@v2
+      - name: Build
+        run: |
+          ./gradlew :app:assembleDebug