Update actions workflow

.github/workflows/build.yml

@@ -0,0 +1,20 @@
+name: "build"
+
+on: ["pull_request", "push"]
+ 
+jobs:
+  build:
+    strategy:
+      matrix:
+        java: ["1.8", "11"]
+        os: ["ubuntu-18.04"]
+    runs-on: "${{ matrix.os }}"
+    steps:
+    - name: "Checkout Repository"
+      uses: "actions/checkout@v2.3.4"
+    - name: "Setup JDK ${{ matrix.java }}"
+      uses: "actions/setup-java@v1.4.3"
+      with:
+          java-version: "${{ matrix.java }}"
+    - name: "Clean Build"
+      run: "./gradlew clean build"