[Renderers/SDL3] Add image rendering and scissor support to SDL3 renderer

[steviegt6]

Implements CLAY_RENDER_COMMAND_TYPE_IMAGE for the SDL3 renderer using SDL_image essentially identically to how it's done in SDL2 (see #208).

Also implements CLAY_RENDER_COMMAND_TYPE_SCISSOR_START/CLAY_RENDER_COMMAND_TYPE_SCISSOR_END based on the similar implementation in the SDL2 renderer.

[steviegt6]

When I first implemented images, the example was split and I just inserted an image to render. Now the SDL3 example uses the video demo and the image example in the SDL2 example also goes unused, I'll leave the loading there as an example but I'm not sure what the ideal change to make it.

[ernestoyaquello]

After it's rendered, the texture should be destroyed here:

Suggested change

	SDL_RenderTexture(renderer, texture, NULL, &dest);
	SDL_RenderTexture(renderer, texture, NULL, &dest);
	SDL_DestroyTexture(texture);

[ernestoyaquello]

Is there a reason why we pass a surface and then convert it into a texture? The SDL_image library allows us to get a texture directly for any image (IMG_LoadTexture, etc), so that seems much more efficient. 🤔

[nicbarker]

Thank you for the great work here, we just get the DestroyTexture in to prevent the memory getting leaked, then we can merge it 😁

[steviegt6]

Thanks for merging; sorry I didn't get to the additional changes myself! I've been busy with work.

[nicbarker]

That's totally fine, thank you for the good work!