Add Nashorn Hello World project

- Gradle 9.5.1 (Groovy DSL) build with java + application plugins
- Nashorn standalone engine (org.openjdk.nashorn:nashorn-core:15.6)
- HelloNashorn.java: runs JS via NashornScriptEngineFactory

src/main/java/com/example/HelloNashorn.java

@@ -0,0 +1,20 @@
+package com.example;
+
+import org.openjdk.nashorn.api.scripting.NashornScriptEngineFactory;
+
+import javax.script.ScriptEngine;
+
+public class HelloNashorn {
+    public static void main(String[] args) throws Exception {
+        NashornScriptEngineFactory factory = new NashornScriptEngineFactory();
+        ScriptEngine engine = factory.getScriptEngine();
+
+        engine.eval("print('Hello World from JavaScript!')");
+
+        String result = (String) engine.eval(
+            "var greeting = 'Hello from Nashorn on JDK ' + java.lang.System.getProperty('java.version');" +
+            "greeting"
+        );
+        System.out.println(result);
+    }
+}