Document upstream source of the "FAQ/Guidelines" asset post

The initial content of this post is automatically populated by the Discourse framework. Knowing the source origin of the
content will allow upstream changes to be pulled into the asset, and generally applicable fixes and enhancements we make
to be pushed back upstream.

Author: per1234

content/categories/staff/_topics/faq-guidelines/README.md

@@ -23,3 +23,4 @@ The stock document is provided as part of the Discourse instance and is not Ardu
 - Page as rendered to users: https://forum.arduino.cc/faq
 - https://forum.arduino.cc/t/how-to-get-the-best-out-of-this-forum/679966
 - https://meta.discourse.org/t/discourse-new-user-guide/96331
+- Upstream source: https://github.com/discourse/discourse/blob/main/config/locales/server.en.yml (in the `en.guidelines_topic` mapping)