Add CI build with GHA

.github/workflows/ci.yml

@@ -0,0 +1,27 @@
+name: ci
+
+on:
+  push:
+  pull_request:
+
+env:
+  MAVEN: ./mvnw
+
+jobs:
+  maven-build:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        java-version:
+          - 17
+          - 21
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-java@v2
+        with:
+          distribution: 'temurin'
+          java-version: ${{ matrix.java-version }}
+          cache: 'maven'
+      - name: Maven build
+        run: |
+          $MAVEN clean install -B