GitHub Actions: enable PR verification

.github/workflows/verify_on_pr.yml

@@ -0,0 +1,29 @@
+name: 'build test deploy'
+
+on: pull_request
+
+jobs:
+  verify:
+    runs-on: ubuntu-latest
+    if: github.repository == 'agrestio/agrest'
+
+    name: JDK ${{ matrix.java }}
+
+    strategy:
+      matrix:
+        java: [ "11", "17", "21" ]
+      fail-fast: true
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v3
+
+      - name: Setup java
+        uses: actions/setup-java@v3
+        with:
+          distribution: 'temurin'
+          java-version: ${{ matrix.jdk }}
+          cache: 'maven'
+
+      - name: Build and test...
+        run: mvn clean verify