[Doc] Add a friend projects section

[JeremyBP]

Hi,

It would be useful to add a doc section talking about some of Refit's "friend" projects.
I mean libraries based on Refit or working with it.

Something like:

Friend projects

• Generating code:
  • REST API Client Code Generator: A collection of Visual Studio C# custom tool code generators for Swagger / OpenAPI specification files, including Refitter.
  • Refitter: Generate the Refit interface and contracts from Swagger / OpenAPI specifications, plus some optional registration helpers with or without Apizr
• Extending features:
  • Apizr: Refit's client resilient manager (fault handling, connectivity checking, cache management, authentication handling, http tracing, priority management, data mapping and more...)
  • Refit.Insane.PowerPack: Refit library extensions which provides attribute based cache and auto-retry features

Let me know if you want me to push a PR and if you know some other libs to be listed here.

[Shen37]

Hello can we have a discussion about this if yes kindly reach to me on my discord by "shen.li"