WIP: Retribute Profiles Spec, initial draft

Human-readable version at https://dev.funkwhale.audio/retribute.me/spec/blob/profiles-spec/specs/retribute-profiles-format.md

I don't expect to merge this anytime soon, but I feel like it was needed to write this down to start the discussion. I'd gladly accept any review, comments and feedback!

This second spec aims at specifying the creator's side of things. The idea is to standardize how Retribute clients retrieve Retribute information, and donation links in particular, once they have suggestions.

I'd probably recommend doing your first reading at https://dev.funkwhale.audio/retribute.me/spec/blob/suggestions-spec/specs/suggestions-feed-format.md, the Suggestions feed specification at !1, and use the review interface for typos/suggestions afterwards :)

Todo:

• Pick a format (JSON-LD, Plain JSON, something else) to represent the data
• Document all the properties (weight, url, providel, avatar, summary, etc.)
• Document (or at least mention) hubs
• Write a PoC in Python (https://github.com/scrapinghub/extruct seems a good candidate) to play with exemples and real websites
• Add a section about security/identity considerations (to avoid following links you shouldn't, this kind of things)
• Everything else