Template cleanup for homepages and docker URLs

[mgorny]

Update the templates to avoid giving dead/unmaintained/confusing links and update the docker URLs:

• remove the links to the public httpbin instances from the legacy template since they're all running the old version or are entirely dead
• use this repository as the "GitHub corner" and homepage
• add/keep a "Kenneth Reitz project" link for the original attribution
• remove bitcoin because the link is dead and the id may no longer be valid
• remove version from "base template" used by swagger while the page is loading because it's unnecessary and an unnecessary maintenance effort
• update the docker instructions in templates based on README

That said, the docker instructions don't really work for me:

$ docker pull ghcr.io/psf/httpbin
Using default tag: latest
Error response from daemon: Head "https://ghcr.io/v2/psf/httpbin/manifests/latest": denied

[kevin1024]

That said, the docker instructions don't really work for me:

Yep I think I still have to do something to make the docker image actually push after @exhuma's changes.

[mgorny]

Thanks for merging! Could you make a new release soonish? We'd use my earlier changes, particularly gevent dep removal.