Voice: Basics

• Add the Litecord Voice Server Protocol (LVSP) docs (docs/ folder)
• Admin API for voice server management (creation of regions and servers), no FE for that, and it already leverages on existing authentication (your discord token serves to access the admin API if you have the staff flag set), documented too! (docs/ folder)
• Typing fixes from mypy!
• Add message.member
• Other varied fixes (lazy guilds, None values in Storage, etc)
• Better (global) fix for message.webhook_id, compared to a7dc9e01

Should we merge this in current form? Once the LVSP docs are over, I mean. We don't have a voice server implementation yet and I'm stuck on implementing anything else other than running around in thought-experiment land.