Add GitHub Actions for Gradle builds

.github/workflows/gradle-build-and-test.yml

@@ -0,0 +1,21 @@
+name: GitHub Actions
+
+on: [ push, pull_request ]
+
+jobs:
+  gradle-build-and-test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: APT Install Java
+        run: |
+          sudo apt-get update && sudo apt-get install openjdk-17-jdk
+          sudo update-java-alternatives --set java-1.17.0-openjdk-amd64
+      - name: Build
+        run: |
+          export JAVA_HOME=/usr/lib/jvm/java-17-openjdk-amd64
+          ./gradlew jar
+      - name: Test
+        run: |
+          export JAVA_HOME=/usr/lib/jvm/java-17-openjdk-amd64
+          ./gradlew test