Feature request: add a cvar that shifts the player skin number that engine displays

[KillianMiles]

I would like to request a feature that can shift player skin that QC tells engine to display to something else.

Use-case: Say QC is using skin=1 for blue team and skin=2 for red team. If i want to give players an option to display various other versions of team skins.

scr_shiftplayerskin 2 would for example add "2" to the skin number on any player model (player.mdl/player.md3) so if QC is telling the engine to show skin 1, it instead shows skin 3 etc