feat(shell): ui-shell header color updates

[aledavila]

Closes#2704

Updates color tokens in shell theme - ONLY HEADER

Changelog

New

• color tokens

Changed

• separated panel tokens to their own

TODO:

• Need to update variables in the .scss files for the side nav, panels, switcher (need to check they are using the correct variables) once designs are in
• Need to update the hover variables hex color to variables names once that is in the elements package

[netlify]

Deploy preview for the-carbon-components ready!

Built with commit 9771004

https://deploy-preview-2721--the-carbon-components.netlify.com

[netlify]

Deploy preview for carbon-components-react ready!

Built with commit 9771004

https://deploy-preview-2721--carbon-components-react.netlify.com

[joshblack]

Hey @aledavila! I think prettier is just off which is causing the CI check to fail. Running this at the top-level should fix it:

yarn format

[tw15egan]

Broke this issue apart into two separate issues, one that will track side nav variable updates and this one that contains header fixes.

Looks great!

👍

#2727 for reference