handle `@import`

[fuzetsu]

Currently zaftig doesn't support @import statements, would it make sense to do so? They only work if they're declared as the first rules in the stylesheet.

So would they only work in z.global? I feel like it probably doesn't make sense to implement, since links work fine, and there's less uncertainty about how they can be included..
Including an external stylesheet kind of goes against CSS in JS anyway...

https://developer.mozilla.org/en-US/docs/Web/CSS/@import

[fuzetsu]

Toyed around with an implementation for this, but I'm not sure if it's worth it.
It behaves a bit strangely in Firefox while in debug mode, and I'm not sure if I see the use at this point.

Until I see a good use case I won't bother adding this.