[Renderers/Raylib] PERF: Fixed many allocations per frame for each string to render.

[hexmaster111]

Updated renderers/raylib/clay_renderer_raylib.c to store the malloc'd buffer, so we dont need to malloc and free every string part.

Also added Clay_Raylib_Close() to free the buffer.

[hexmaster111]

I just looked through the examples, and it looks like we are missing a few calls to CloseWindow() in raylib, If this is merged, ill update the raylib examples to call Clay_Raylib_Close() to de-init raylib, as well as free the stored buffer.