Enable GitHub actions

Author: tananaev

.github/workflows/gradle.yml

@@ -0,0 +1,20 @@
+name: Java CI with Gradle
+
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+    branches: [ master ]
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v2
+    - uses: actions/setup-java@v1
+      with:
+        java-version: 1.8
+    - run: chmod +x gradlew
+    - run: ./gradlew build