Set up test workflow

.github/workflows/maven.yml

@@ -0,0 +1,29 @@
+name: 'build test'
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ '*' ]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    strategy:
+      matrix:
+        java: [ 11, 17, 21 ]
+
+    steps:
+      - name: Checkout...
+        uses: actions/checkout@v4
+
+      - name: Set up JDK...
+        uses: actions/setup-java@v4
+        with:
+          java-version: ${{ matrix.java }}
+          distribution: 'temurin'
+          cache: 'maven'
+
+      - name: Build and test...
+        run: mvn clean verify -U