Feature: port Logic_skill from mapbase

[kiddu25]

Which component should be improved?

Gameplay

Describe your feature suggestion in more detail

logic_skill is a entity logic who reads the game's current difficulty level and detects when it changes.
when the difficulty level from hl2 will be port into p2ce,(which iirc isn't the case) i feel like this entity could be interessing for puzzle situation etc

code and fgd :
https://github.com/mapbase-source/source-sdk-2013/blob/master/sp/src/game/server/mapbase/logic_skill.cpp

https://github.com/mapbase-source/source-sdk-2013/blob/6cc2937f5a1aa5bf60e0ca5af96a0324b0e525dc/sp/src/game/shared/gamerules.cpp#L701

https://github.com/TeamSpen210/HammerAddons/blob/81f2bc234731cc77c1c7a1de6ae2282e847f5196/fgd/point/logic/logic_skill.fgd#L4