Adding resource mapping example that copies all sub folders and maintains folder structure

docs/en/UI/AspNetCore/Client-Side-Package-Management.md

@@ -95,6 +95,7 @@ mappings: {
     "@node_modules/bootstrap/dist/css/bootstrap.css": "@libs/bootstrap/css/",
     "@node_modules/bootstrap/dist/js/bootstrap.bundle.js": "@libs/bootstrap/js/",
     "@node_modules/bootstrap-datepicker/dist/locales/*.*": "@libs/bootstrap-datepicker/locales/"
+    "@node_modules/bootstrap-v4-rtl/dist/**/*": "@libs/bootstrap-v4-rtl/dist/"
 }
 ````