maven.yml: add app execution

Author: stephengold

.github/workflows/maven.yml

@@ -29,3 +29,8 @@ jobs:
         cache: maven
     - name: Build with Maven
       run: mvn -B package --file pom.xml
+    - name: Execute the HelloWorld app
+      run: |
+        $JAVA_HOME/bin/java --enable-preview \
+          -cp target/JoltPhysics-JavaFFM-5.5.0-jar-with-dependencies.jar \
+          volucris.bindings.jolt.HelloWorld