Command execution timeouts

[timedoutuk]

Is your feature request related to a problem? Please describe.
It would be handy to be able to limit the maximum runtime of commands, both globally and locally. This could allow, for example, a 10 minute cap on long running commands that rely on something user-provided or network based.

Describe the solution you'd like
Ideally, a global command_execution_timeout option in NioBot, and an @niobot.max_runtime decorator for individual commands

Describe alternatives you've considered
There aren't really any aside from wrapping the command execution manually