Import color design tokens from design token library

[georgewrmarshall]

Description
Now that the new color style naming conventions have been decided on, we can start adding them to the code base. These variables will be color agnostic, theme compatible and semantically correct. This would be the first stage of making sure we are using consistent colors across the app and make all of our styles theme ready.

The end goal is for the design tokens to be updated in Figma, pushed to the design-tokens repo and then updated in the different apps. For MVP we can add the css vars and automate the process in future.

Technical Details

• import design token stylesheet from @metamask/design-tokens repo
• create documentation for their use in storybook