Registers a custom cvar (temporarily).
C_CVar.RegisterCVar("name" [, value])
- string - name of the custom CVar to set.
- string (optional) - init value of the CVar, any number will be saved as a string.
- You can register your own CVars. They are set game-wide and will persist after relogging/reloading but not after closing the game.
- Patch 8.1.5 (2019-03-12): Moved to C_CVar. The previous alias RegisterCVar is still available as a script wrapper. 
- Patch 1.2.0 (2004-12-18): Added.