feat: implement avatar decorations

[Victorsitou]

Summary

Implements https://github.com/discord/discord-api-docs/pull/5723, ~~the x-super-properties header in http.py is only to receive animated avatar decorations, Discord should fix that (probably?)~~

Checklist

• [x] If code changes were made, then they have been tested
  • [x] I have updated the documentation to reflect the changes
  • [x] I have formatted the code properly by running task lint
  • [x] I have type-checked the code by running task pyright
• [ ] This PR fixes an issue
• [x] This PR adds something new (e.g. new method or parameters)
• [ ] This PR is a breaking change (e.g. methods or parameters removed/renamed)
• [ ] This PR is not a code change (e.g. documentation, README, ...)

[onerandomusername]

@Victorsitou would you please resolve conflicts?

[shiftinv]

Looks like this change was lost in one of the merges: https://github.com/DisnakeDev/disnake/pull/889/files/b187544b929a62d5ab8070e7c4d54124291ea5e5#diff-0ee295c29def16f570f86378eff8ba37315e464d415e731d5d8ea2e67ce16f68R5593

Other than that, testing this is unfortunately a bit difficult right now, since there's no general rollout yet :/

[Victorsitou]

Fixed in 74f7ad0543fc2050159e4fee193028f03aaaafce.

[shiftinv]

As expected, the API for this has changed slightly: https://github.com/discord/discord-api-docs/pull/6464/files#diff-9c0465597400a1bfff16968024a03ed3e42f9f35b43b9d4419bb0156d47ff9d2 While we have no immediate use for the sku_id field, storing the raw avatar_decoration_data dict (instead of just the asset field) would be the most future-proof solution.

[Victorsitou]

As expected, the API for this has changed slightly: https://github.com/discord/discord-api-docs/pull/6464/files#diff-9c0465597400a1bfff16968024a03ed3e42f9f35b43b9d4419bb0156d47ff9d2

I've updated the PR to match the actual API.