stdinc: Added missing `\param` to SDL_CreateEnvironment.

include/SDL3/SDL_stdinc.h

@@ -1032,7 +1032,9 @@ extern SDL_DECLSPEC SDL_Environment * SDLCALL SDL_GetEnvironment(void);
 extern SDL_DECLSPEC void SDLCALL SDL_CleanupEnvironment(void);
 
 /**
- * Create a set of environment variables
+ * Create a set of environment variables.
+ *
+ * \param populated SDL_TRUE to initialize it from the C runtime environment, SDL_FALSE to create an empty environment.
  *
  * \returns a pointer to the new environment or NULL on failure; call
  *          SDL_GetError() for more information.