Multiple typing issues

[0x5c]

This is an issue to list all currently found typing and typing-related issues in qrm that will require refactoring, or depend on Bolt features..

• 1. Mypy is mad each time we access bot.qrm or a member of such

• 2. Mypy is mad when we set a category in the command/group decorator

• 6. Error handling: mypy is angry that we try to append something to embed.description

• 7. globalchannelconverter: yells that a method is missing yet present from class

• 8. "": "TYPE MISMATCH"

[0x5c]

Those are the easy to fix ones

• 3. extctl: Mypy does not like that we call the result of get_command(), perhaps we could call it directly
• 4. add_react(): the type is too strict
• 5. error handling: ctx.invoked_with could be None
• 9. embedfactory: mypy does not like like directly passing ctx.author as text=
• 10. addreact: none has no id

Breaking up into another issue: #289