add a max volume setting

[hamilton5]

Is your feature request related to a problem? Please describe.
no

Describe the solution you'd like
don't allow users to set !volume 100, limit it to x

Describe alternatives you've considered
no options.

Additional context
I've found clipping happens at 100, I like to keep it around 30-40, some users might be trolling or for what ever reason, only allow a value lower then 'max'

[TerryGeng]

Reasonable. Will do.