doc: sunset, make maint status clear

[koivunej]

This PR will record the maintenance status, strip out funding/sponsoring things, so that we can archive the repository for now. I hope I didn't miss anything.

[b5]

Sorry to see this change, but I very much appreciate taking the time to clarify the status of this project.

For others who need IPFS in rust, we're working on iroh, and would be happy to chat.

To the rust-IPFS maintainers, I'd love to take some time to chat about did & did not work on this project, ideally so we can all grow & learn.

Thanks so much for your efforts!

[koivunej]

@b5 we do have one interested in picking up maintainership, so I guess we are a bit in a holding pattern.

I can be reached from the commiter email address for any discussions with the disclaimer that I haven't yet peeked at iroh.

[dariusc93]

Thats unfortunate. Been doing passive maintenance on my own fork of rust-ipfs though do feel there could be more work done.

Thanks for all the work you have done though!