Add Notepad++ Bicep Syntax Highlighting Information (#16506)

Add Notepad++ Bicep Syntax Highlighting User Defined Language (UDL)
link.

This documentation is only available on GitHub and not on the learn
website so I'm only updating it in this repo.
###### Microsoft Reviewers: [Open in
CodeFlow](https://microsoft.github.io/open-pr/?codeflow=https://github.com/Azure/bicep/pull/16506)

Author: richardsondev

docs/highlighting.md

@@ -90,4 +90,7 @@ npx http-server ./src/monarch/test/baselines
 ```
 
 ## Prism.js
-Bicep has a community-contributed [Prism.JS](https://prismjs.com/) highlighter available [here](https://github.com/PrismJS/prism/blob/master/components/prism-bicep.js).
+Bicep has a community-contributed [Prism.JS](https://prismjs.com/) highlighter available [here](https://github.com/PrismJS/prism/blob/master/components/prism-bicep.js).
+
+## Notepad++
+A community-contributed User Defined Language (UDL) file for Bicep syntax highlighting in [Notepad++](https://notepad-plus-plus.org/) is available [here](https://github.com/richardsondev/azure-bicep-udl).