[Core] UserData for Clay_SetMeasureTextFunction

[emoon]

So this function

void Clay_SetMeasureTextFunction(Clay_Dimensions (*measureTextFunction)(Clay_String *text, Clay_TextElementConfig *config));

There is no userData being passed to compared to the callback to

void Clay_OnHover(void (*onHoverFunction)(Clay_ElementId elementId, Clay_PointerData pointerData, intptr_t userData), intptr_t userData);

I wonder if it would make sense to add that?