feat(grid): new light/dark mode colors

[jzempel]

Description

Completed recolor work for Pane.Splitter, Pane.SplitterButton and <Grid debug>

Checklist

• 👌 design updates will be Garden Designer approved (add the designer as a reviewer)
• 🌐 demo is up-to-date (npm start)
• ⬅️ renders as expected with reversed (RTL) direction
• 🤘 renders as expected with Bedrock CSS (?bedrock)
• 💂‍♂️ includes new unit tests. Maintain existing coverage (always >= 96%)
• ♿ tested for WCAG 2.1 AA accessibility compliance
• 📝 tested in Chrome, Firefox, Safari, and Edge

[lucijanblagonic]

Pane.SplitterButton seems to have a light mode shadow in dark mode. It should be 88% / 1100, and not 16% / 200.

Current vs. updated example on red background to make it clearer.

[jzempel]

Pane.SplitterButton seems to have a light mode shadow in dark mode. It should be 88% / 1100, and not 16% / 200.

Thanks, @lucijanblagonic. I've updated here and left a comment in Figma.

[geotrev]