Create index(es) of useful implementation libraries

[andypiper]

I think we should look at a couple of lists:

• libraries and SDKs to work with common ActivityPub and/or other protocols, per language
• frameworks for building lightweight and extensible AP servers, e.g. Fedify, Darius' node one, etc.

Some common starting points for developers looking to build things. not service-specific, so not the same as the list of Mastodon-compatible client libraries on their docs page, for instance.

[andypiper]

https://github.com/jointakahe/taktivitypub
https://unstable.fedify.dev/
https://github.com/dariusk/express-activitypub