Add support for css vars

[ChildishGiant]

[aksmfosef11]

#75

This is not possible for variables that are dynamic
It is possible to use frequently used color name fixed.

[muuvmuuv]

Uff, highly needed. Wonder why this isn't natively integrated into Code. Anyone working on this already?

[v1adko]

I think it could be done if you explicitly add the color definitions into extension settings, or in a specific json file that the extension could read, but I doubt that the real dynamic color definitions could be achieved (like for theming) as code analysis would be too complex or too slow. Even global lookup of all :root definitions could be slow depending on the size of the codebase.

[muuvmuuv]

This is something that could run when in idle. Onced parsed then cached and if a scss, css file is edited this one gets parsed again.

[wesbos]

VS Code knows the colour of the variable if it's in the same file. Is it possible to see how they do it?