Check user ban status for commands

**Is your feature request related to a problem? Please describe.**

When a user is banned in AlveusSanctuary, they can still run commands (if they have permissions) in the AlveusGG chat, and via the API integration.

**Describe the solution you'd like**

In the Twitch connection class, maintain a set of banned users (https://twurple.js.org/reference/api/classes/HelixModerationApi.html#getBannedUsers) for the main channel that refreshes itself every x minutes. In the chat message handler, always check the user is not in the banned list before processing their message.

**Describe alternatives you've considered**

N/A

**Additional context**

N/A