Add missing SDL_BlendMode values

Author: Susko3

SDL3-CS/SDL3/SDL_blendmode.cs

@@ -11,7 +11,9 @@ public enum SDL_BlendMode : UInt32
     {
         SDL_BLENDMODE_NONE = SDL3.SDL_BLENDMODE_NONE,
         SDL_BLENDMODE_BLEND = SDL3.SDL_BLENDMODE_BLEND,
+        SDL_BLENDMODE_BLEND_PREMULTIPLIED = SDL3.SDL_BLENDMODE_BLEND_PREMULTIPLIED,
         SDL_BLENDMODE_ADD = SDL3.SDL_BLENDMODE_ADD,
+        SDL_BLENDMODE_ADD_PREMULTIPLIED = SDL3.SDL_BLENDMODE_ADD_PREMULTIPLIED,
         SDL_BLENDMODE_MOD = SDL3.SDL_BLENDMODE_MOD,
         SDL_BLENDMODE_MUL = SDL3.SDL_BLENDMODE_MUL,
         SDL_BLENDMODE_INVALID = SDL3.SDL_BLENDMODE_INVALID,