use ColorAdd render style for Revenant fireball to match UZDoom (#1616)

Author: nstlaurent

Assets/Assets/Actors/Doom/Monsters/Revenant.txt

@@ -67,6 +67,7 @@ actor RevenantTracer
     SeeSound "skeleton/attack"
     SpawnID 53
     Speed 10
+    RenderStyle ColorAdd
 
     PROJECTILE
     +RANDOMIZE

RELEASENOTES.md

@@ -48,4 +48,5 @@
 - Removed sprite overlap code from CPU and use sprite detph bias on GPU instead to fix z-fighting.
 - Add support for transparent rendering in static shader.
 - Add pool for entity sprite VBO/VAOs to fix stutter when encountering a new sprite to render.
-- Update order independent transparency weight to be more stable across a higher range.
+- Update order independent transparency weight to be more stable across a higher range.
+- Use ColorAdd render style for Revenant fireball to match UZDoom.