Absence of documentation to extend WinUI3 app with optional packages and Related Sets using dotnet

There seems to be no accurate and recent documentation on the internet on how to extend a WinUI3 app with optional packages and Related Sets using dotnet.

Overview of optional packages link:
[https://learn.microsoft.com/en-us/archive/blogs/appinstaller/uwpoptionalpackages](https://learn.microsoft.com/en-us/archive/blogs/appinstaller/uwpoptionalpackages)

Start by reviewing the archived Optional Packages overview linked in the issue and the current WinUI3 and dotnet documentation. Determine how optional packages and Related Sets should be documented for a WinUI3 app, then produce accurate, recent guidance covering the setup and usage steps.

Written by the indexing model from the issue text.