[FEATURE REQUEST] LCD Brightness GCode support

[PartemImperium]

If it makes sense, enter what type of printer or upgrade the feature request applies to. Printer type - MK3S, MK3 MMU Upgrade - N/A

Is your feature request related to a problem? Please describe. Back in 3.9.0 support was added to control the brightness of the LCD on MK3's. It would be nice if support could be added to control the brightness of the LCD through GCode.

Describe the solution you'd like It looks like there is M256 in the marlin docs reserved for LCD brightness https://marlinfw.org/docs/gcode/M256.html.

[github-actions[bot]]

This issue has been flagged as stale because it has been open for 60 days with no activity. The issue will be closed in 7 days unless someone removes the "stale" label or adds a comment.

[3d-gussner]

@PartemImperium Thanks for the request. I can't promise if that will be implemented but assigned it to myself as a reminder.