feat: message forwarding

[NeloBlivion]

Summary

Implements message forwarding, alongside some small cleanups for other message features.

Information

• This PR fixes an issue.
• 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, typehinting,
  examples, ...).

Checklist

• I have searched the open pull requests for duplicates.
• If code changes were made then they have been tested.
  • I have updated the documentation to reflect the changes.
• If type: ignore comments were used, a comment is also left explaining why.
• I have updated the changelog to include these changes.

[NeloBlivion]

more or less done, just need to add mention/role mention handling and partialmessage support... but still 403ing on my bot 😔

[Lulalaby]

unlucky bcs its 95% out. you're in th holdout group. try making a new bot