Allow user to choose the number of consumer threads that send messages to discord

[abrahammurciano]

If a user logs too often the queue will grow much faster than it can be dequeued. One possible solution is to use more consumer threads.

• [x] check if more threads improves performance
• [ ] if so, add parameter for number of threads in DiscordHandler

[abrahammurciano]

More threads does nothing. Can't consume faster than Discord's API allows us to send messages anyways. That's pretty slow.