[Upgrade] Add BC player entry limit setting in server-side (Season 6)

Hello,

Would be really nice to finally add new setting for BC Event, so player entry limit count can be changed on server-side by admin.
This is one of the most things players are "kinda" complaining/suggesting to change and in my scenario increase/add more entry slots for this event (in my case, I want to change to = 20).

Same config style as DS Event have this config in "/IGCData/Events/" folder IGC_DevilSquare.ini file, could be added to IGC_BloodCastle.ini as well, like:

;-----------------------------------------------------------
;-- Maximum Players per Blood Castle room
;-----------------------------------------------------------
BloodCastleMaxPlayerPerRoom = 20

Let me know what you think, thanks ! ?