Add SVG import.

[chris-ryu]

Please support import of SVG file format.
I hope I can generate code right from the designer work results.

[migueldeicaza]

Idea: we could use either the SVG importer that we are using now in SkiaSharp.Svg which is a partial implementation of Svg, but it has a license friendly to be used in stores, or we could bind librsvg which is more advanced and supports plugging your own "backend" but is LGPL.

Given that Kimono is not a library, it could use librsvg