Add section for CSS vars to GH pages about calcite-colors

[julio8a]

Thanks for opening this issue @jcfranco.
I think we should prioritize showing the CSS vars or SASS vars over all the colors in the library, which are not as helpful.

[kyle-03674]

I agree with @julio8a. However, I'm hoping we can still show the entire set, maybe lower on the page or minimized? It serves a secondary, more minor purpose for designers who want to access all the colors to add some directly into artwork. Again, my use case is thinking in the broader sense of "any designer," including those not using 'calcite colors.' Which is likely outside the primary purpose for this page. So if it doesn't work out, it's okay. :)

[julio8a]

At this point, we should not proceed with this. Everything color vars will be presented on the colors page on developers.
https://developers.arcgis.com/calcite-design-system/foundations/colors/