Update Table of Contents to use new color theme variables

[pastelcyborg]

Done

• Replaced old color variables with new color theme variables for improved theming support

Fixes WD-11872

QA

• Open Table of Contents demo
• Verify Table of Contents appears as expected (with slight, intentional change to bottom border color)

Check if PR is ready for release

If this PR contains Vanilla SCSS code changes, it should contain the following changes to make sure it's ready for the release:

• PR should have one of the following labels to automatically categorise it in release notes:
  • Feature 🎁, Breaking Change 💣, Bug 🐛, Documentation 📝, Maintenance 🔨.
• Vanilla version in package.json should be updated relative to the most recent release, following semver convention:
  • if CSS class names are not changed it can be bugfix release (x.x.X)
  • if CSS class names are changed/added/removed it should be minor version (x.X.0)
  • see the wiki for more details
• Any changes to component class names (new patterns, variants, removed or added features) should be listed on the what's new page.

Screenshots

[webteam-app]

Demo

Jenkins

demos.haus

[jmuzina]

Looking good on code/qa side of things - we should check with @lyubomir-popov on the color of the bottom border just to be sure

[lyubomir-popov]

yes, the low contrast var is correct for all hrs but the ones at the top of sections - right above the h2s. Can we add this somewhere in the hr documentation please (separate task of course)?

[jmuzina]

@pastelcyborg I found this page and realized we should probably make sure we keep it updated as we add theming support to these older components.

It is templates/docs/settings/color-settings.md.

Edit: disregard; updating this page is unneeded

[bartaz]

Looks good, thanks!