PlayerCmd Port

I decided to recreate the PlayerCmd hook that was originally created by Lat for SRB2 Kart and had a merge request that was made by Steel to port it into vanilla in the SRB2Internal repo. The main purpose of this hook is to run local code that can be used for custom menus and other useful client-sided purposes.

Test files: srb2_playercmdporttest.exe PlayerCmdPortTest.lua