Pull in rrectv work

[crertel]

This finishes pulling in @GPrimola 's work that I merged in #17 .

We'll rebase here and have staging ground to pull in the functionality to the Cairo backend too.

[crertel]

Ah, hell's bells...okay @ringlej I'm caught back up on this--is there any chance you can grab the Cairo side of this, or should I grab it? I think you've got a bit more context there than I do.

[ringlej]

The only thing I'd mention here is that there isn't a Cairo implementation provided so anyone using it with Cairo will get a log message if the function is attempted with no rendering done.
That said, I'd rather this not hold up a release.

[ringlej]

Right now I don't have the cycles to tackle this for Cairo.

[crertel]

Makes sense. Let's do a fast-follow then.

(let's here == "Chris will give it a shot later". not trying to give you work!)

[GPrimola]

@crertel @ringlej I can do it for Cairo too! I'm almost sure when I did it for NVG there wasn't support for Cairo yet. Maybe? 🤔
Anyway, will do it in another PR.
Thanks!! :)

[crertel]

'preciate ya, @GPrimola!