[Bug] CSS root is not patched correctly on webpages

[SpaceEnergy]

Before Reporting

• [X] I found no existing issues matching my bug
• [X] My issue is not caused by the Millennium interface inside Steam (Themes, Plugins & Update Panel). If it is, make a issue report in this repo.
• [X] My issue is not caused by a theme

Describe the Bug

CSS root colors are displayed in the DevTools but are not recognized by CSS and are therefore greyed out

Expected Behavior

The CSS should recognize the variable and use its color

Steps To Reproduce

1. add a variable color for the scrollbar
2. use "RootColors": "" in skin.json
3. open the store page or steamcommunity.com in Steam and have a look at the scrollbars

Operating System

Windows

Anything else?