Add TryParseSvgPath functionality

[JimBobSquarePants]

I think it would be an invaluable feature for our PathBuilder type to be able to parse an SVG paths.

We could add a method with the following signature.

bool TryParseSvgPath(ReadonlySpan<char> path, out bool value);

We can use the Skia SkPath.FromSVGString method as inspiration.

https://github.com/google/skia/blob/5deac304821b04176c0c3ac9535e5889a2966265/src/utils/SkParsePath.cpp#L75-L203

Note. We follow the System.Drawing API model for our PathBuilder type. Skia uses a different model that includes MoveTo LineTo methods so we would need to translate that across.

[tocsoft]

FYI the BaseGlyphBuilder works in that same builder model with the MoveTo/LineTo style so that code could probably be hoisted into a shared component/PathBuilder wrapper type that exposes that API publicly and we would just utilise it in the glyph builder rather than implementing it there directly.

[tocsoft]

#206 should do it... we probably have some missing api/cases as those are just the ones we can utilise for GlyphRendering but we can expand as required.

That's the class I would hand the SVG path parsing logic off too (at least as an extension method).

[JimBobSquarePants]

Thanks, will have a proper look. This will be super useful for drawing text along a path.

[JimBobSquarePants]

@tocsoft I'll finish off your branch and do a PR now that we have ArcTo.

[JimBobSquarePants]

Yep, Nope. I can't read that C++ it's nightmarish.

[tocsoft]

#217 is a mostly working version... has an outstanding issue on T commands https://svgwg.org/specs/paths/#PathDataQuadraticBezierCommands but its actually parsing/compiling with a few test cases i've lifted from the SVG specs themselves.