Accept JS file as argument and support NPM modules via jvm-npm

- HelloNashorn now takes a JS file path as command-line argument
- Uses jvm-npm (org.bsc:jvm-npm-core:1.1.0) for require() support
- Require.root set to script's parent dir so node_modules resolves correctly
- Engine created with -scripting mode for load() support

build.gradle

@@ -9,6 +9,7 @@ repositories {
 
 dependencies {
     implementation 'org.openjdk.nashorn:nashorn-core:15.6'
+    implementation 'org.bsc:jvm-npm-core:1.1.0'
 }
 
 application {