ci: add GitHub Action for Gradle Build

Author: netmikey

.github/workflows/build.yaml

@@ -0,0 +1,24 @@
+name: Java CI
+
+on: [ push, pull_request ]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        java: [ '8', '11', '17' ]
+    name: Java ${{ matrix.java }} sample
+    steps:
+      - uses: actions/checkout@v2
+      - name: Set up JDK
+        uses: actions/setup-java@v2
+        with:
+          java-version: ${{ matrix.java }}
+          distribution: 'temurin'
+      - name: Validate Gradle wrapper
+        uses: gradle/wrapper-validation-action@v1
+      - name: Build with Gradle
+        uses: gradle/gradle-build-action@v2
+        with:
+          arguments: build