[Build] Migrate to GitHub actions

.github/workflows/ci-build.yml

@@ -0,0 +1,13 @@
+name: CI Build
+on: [ push, pull_request ]
+jobs:
+  gradle:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/setup-java@v1
+        with:
+          java-version: 8
+      - uses: eskatos/gradle-command-action@v1
+        with:
+          arguments: build