[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]

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.

[3d-gussner]

Created #4851 it cost quite a bit of resources.

[github-actions]

Thank you for your contribution to our project. This issue has not received any updates for 60 days and may be considered "stale." If this issue is still important to you, please add an update within the next 7 days to keep it open. Administrators can manually reopen the issue if necessary.