Add a simple CI pipeline (now that it is free for public repo)

.github/workflows/test.yml

@@ -0,0 +1,14 @@
+name: Build
+
+on: [ push ]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+    - name: Checkout sources
+      uses: actions/checkout@v4
+    - name: Setup Gradle
+      uses: gradle/gradle-build-action@v3
+    - name: Compile and run unit tests
+      run: ./gradlew test