GH actions: added GraalVM tests

Author: rashtao

.github/workflows/maven.yml

@@ -20,14 +20,29 @@ jobs:
         java-version:
           - 8
           - 11
-          - 15
+          - 16
 
     steps:
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v2
       - name: Set up JDK
-        uses: actions/setup-java@v1
+        uses: actions/setup-java@v2
         with:
+          distribution: 'zulu'
           java-version: ${{ matrix.java-version }}
+          cache: 'maven'
+      - name: Info
+        run: mvn -version
+      - name: Test
+        run: mvn -e --no-transfer-progress test
+
+  # test behavior comparing to JSON.stringify() and JSON.parse()
+  test-graavm:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@latest
+      - uses: DeLaGuardo/setup-graalvm@4.0
+        with:
+          graalvm: '21.2.0'
       - name: Info
         run: mvn -version
       - name: Test