Additive lighting (#685)

* Additive lighting

* adds options for all your optional needs

* one last tiny adjustment before we hit the create pr button

* spaghetti condensing

* add ccvar

* overlight correction

* fix requested changes

* cvar fix

* last fix

* nice

---------

Co-authored-by: deathride58 <deathride58@users.noreply.github.com>
Co-authored-by: MetalSage <metalsage.official@gmail.com>
Co-authored-by: Ed <96445749+TheShuEd@users.noreply.github.com>
Co-authored-by: Ed <edwardxperia2000@gmail.com>

Content.Client/Entry/EntryPoint.cs

@@ -12,6 +12,7 @@ using Content.Client.IoC;
 using Content.Client.Launcher;
 using Content.Client.Lobby;
 using Content.Client.MainMenu;
+using Content.Client.Overlays;
 using Content.Client.Parallax.Managers;
 using Content.Client.Players.PlayTimeTracking;
 using Content.Client.Radiation.Overlays;
@@ -159,6 +160,7 @@ namespace Content.Client.Entry
 
             _parallaxManager.LoadDefaultParallax();
 
+            _overlayManager.AddOverlay(new CP14BasePostProcessOverlay()); // CP14-PostProcess
             _overlayManager.AddOverlay(new SingularityOverlay());
             _overlayManager.AddOverlay(new RadiationPulseOverlay());
             _chatManager.Initialize();