Add support for colors added via theme.json #3373

Is your feature request related to a problem? Please describe.

• Yes users have been asking support for colors added via theme.json
• Issues related:
  • https://www.notion.so/Leticia-Shaw-149584f29f4c8079a1cbf418463c3cc4
  • https://wordpress.org/support/topic/theme-colors-support/

Describe the solution you'd like

• Add support for colors added via theme.json
• Users also mentioned:

  I am expecting it to show as something like "background-color: var(--wp--preset--color--secondary);". Which how the rest of core colors are showing with native Gutenburg blocks.

Describe alternatives you've considered

• Add the theme.json colors as global colors using the hex code