Feat. Add Stickers

[Droid00000]

Summary

Add support for the sticker API.

Added

• API calls for stickers.
• API calls for sticker packs.
• Method to return the sticker objects from a message.
• Method to check if any stickers were used in a message.
• Method to return sticker objects in a server.
• Method to return the maximum amount of stickers a server can have based on boost level.
• Method to check if any stickers have been added to a server.
• Method to return the file URL of a sticker.
• Abstractions to create, update, and delete stickers from a server.
• Abstraction to resolve, or return a full sticker object given the ID.
• Abstraction to resolve or return a sticker pack object.
• Audit log entries for stickers.
• Sticker class, and methods to read attributes.
• Sticker pack class, and methods to read attributes.
• Raw JSON example of a sticker object.

[Droid00000]

Closing this as well since it's a bit of a mess.