Refactored some code from !27, fixed a few bugs, added support for bridging webhook messages.

• Fixed a bug where the bot would allow @here and @everyone pings.
• ​Fixed a bug where the usernames would show \_ instead of _.
• (Hopefully) Fixed a bug where sometimes the URL used for username highlighting would be invalid.
• Refactored the code related to the previous point (removed 2 Clippy warnings it introduced and made it way more readable).
• The bot now also bridges webhook messages often utilized by X -> Discord bridge bots (Like the Matrix bridge we use).
• Rustfmt changed it's mind on a few LOC, so there's a commit with that too.
• Improved comments on some of the code.
• Made debug builds usable, for real this time (spent some time with cargo flamegraph and testing the settings).