option for portal ghosting

[ThisAMJ]

by default you turn off the portal ghost cvars, this should be optional

https://discord.com/channels/146404426746167296/1390594695310344212/1390594695310344212

[aIIison]

i don't think i mess with the cvars, its most likely me messing up the draw buffers somehow here: https://github.com/icyytears/p2fx/blob/master/src/Modules/ShaderApi.cpp#L58

anyway i think this issue is low prio