Add ci workflow

.github/workflows/ci.yml

@@ -0,0 +1,28 @@
+name: CI
+
+on:
+  workflow_dispatch:
+  push:
+    branches:
+      - 2.3.x
+  pull_request:
+    branches:
+      - 2.3.x
+
+jobs:
+  build:
+
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        os: [ubuntu-latest]
+        java: [1.8, 11]
+
+    steps:
+    - uses: actions/checkout@v2
+    - name: Setup JDK
+      uses: actions/setup-java@v1
+      with:
+        java-version: ${{ matrix.java }}
+    - name: Build with Gradle
+      run: ./gradlew clean build