Add SkiaSharp GPU-backed support

[wieslawsoltes]

Enabling easy use of SkiaSharp in MewUI would enable porting / implementing controls/libraries like Svg rendering support (e.g. https://github.com/wieslawsoltes/Svg.Skia) , while it adds a lot of dependencies it could be optional for users to use.

[al6uiz]

Thanks for the suggestion!

I am not sure whether you had a chance to read the article below, but whether to adopt SkiaSharp as the backend was one of the major design questions for me from the very beginning of this project.

https://dev.to/al6uiz/i-wanted-to-ship-a-gui-without-the-net-runtime-two-months-with-mewui-a-cross-platform-ui-17ae

In terms of performance, feature coverage, stability, and reliability, it was certainly a very attractive option. But my biggest concern has always been size. MewUI started with a fairly specific goal: making small NativeAOT-based GUI utilities easy to ship without requiring a separate .NET runtime installation, while keeping the deployment footprint as small as possible.

Once SkiaSharp, together with its .NET bindings and native dependencies, is added, it adds more than 10 MB. That is already well outside the range I originally had in mind — under 10 MB, and ideally closer to 5 MB.

So for me, adopting SkiaSharp is ultimately a question that also touches on the identity of MewUI itself. If I ever find myself considering that direction, then it may simply make more sense to use something like Avalonia with a Fluent-style C# markup approach instead.

It may be something worth revisiting later, but for now I think it makes sense for MewUI to stay on its current path.
(Still, it is true that it remains an appealing option to me😂)

[wieslawsoltes]

@al6uiz Yes I read this, I actully don't need SkiaSharp be integrated into project, the only thing needed is ability to easily plug in into GPU rendering pipleline for fast zero copy and texture sharing for maximum performance. You can see in #117 that I attempted to refactor some parts to make it work and all SkiaSharp parts are in separate projects that came be moved to my separate repository, that's not a problem to maintain and ship separately. I think its great benefit if MewUI has great api to enable integration with UI for other rendering / graphics libraries, it also makes implementing things like GPU based Media Player much easier.