Move gl-dark class to root element
gitlab-ui!3724 (merged) adds automation to design token generated output to include .gl-dark class on :root selector as :root.gl-dark { ... }.
Currently GitLab has .gl-dark on the <body> element. This should be moved to <html> to enable design token CSS custom properties to be imported from gitlab-ui and replace custom CSS custom properties in dark_mode_overrides.scss.
Edited by Scott de Jonge