prepare forked libraries for versioned use

[mayel]

1. PR upstream when possible/relevant
2. if upstream merges and releasing a new version, use that
3. otherwise rename the fork and release to hex.pm, use that

here are some examples:

• https://github.com/bonfire-networks/fetch_favicon
• https://github.com/bonfire-networks/furlex
• https://github.com/bonfire-networks/paginator
• https://github.com/bonfire-networks/ecto_shorts
• https://github.com/bonfire-networks/http_signatures (see also https://akkoma.dev/AkkomaGang/http_signatures)
• https://github.com/bonfire-networks/linkify (see also https://akkoma.dev/AkkomaGang/linkify)