Add "Set Refresh Rate" in Monitor Control

[avaera8775]

Is your feature request related to a problem? Please describe. It would be neat if we had a selection to set a custom Refresh Rate with xrandr, just like we can configure a lot of other things in Linutil for xrandr.

Describe the solution you'd like Similar to the other scripts for monitor options, simply list the top 5 or 10 available refresh rates for current resolution.

Describe alternatives you've considered

Additional context I've attempted this on my own, but for some reason I never can manage to get a clear output on available refresh rates in bash. It might be a skill issue though.