improve bot instantiation

[TobiasGoetz]

Is your feature request related to a problem? Please describe. Improve bot instantiation and cog loading

Describe the solution you'd like

• [ ] Use a class for the bot and run async loop differently (https://discordpy.readthedocs.io/en/stable/migrating.html#asyncio-event-loop-changes)
• [ ] Change cog loading to use add_cog instead of load_extension (https://discordpy.readthedocs.io/en/stable/ext/commands/cogs.html?highlight=cogs#cog-registration)
• [ ] Split initialization and bot code

Describe alternatives you've considered A clear and concise description of any alternative solutions or features you've considered.

Additional context Add any other context or screenshots about the feature request here.