feat(web-components): new slate tokens for conference chat

[futurethang]

RE: #940

Description

Add light/dark tokens.

Related Issue

Motivation and Context

How Has This Been Tested?

Screenshots:

Before (If applicable):

After:

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Other... Please describe:

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[codecov]

Codecov Report

Merging #941 (bec2170) into master (b1d79e7) will decrease coverage by 0.01%.
The diff coverage is n/a.

❗ Current head bec2170 differs from pull request most recent head 7986812. Consider uploading reports for the commit 7986812 to get more accurate results

@@            Coverage Diff             @@
##           master     #941      +/-   ##
==========================================
- Coverage   94.30%   94.29%   -0.02%     
==========================================
  Files         132      132              
  Lines       17120    17120              
  Branches     2521     2521              
==========================================
- Hits        16145    16143       -2     
- Misses        975      977       +2     

Impacted Files	Coverage Δ
web-components/src/components/list/ListItem.ts	97.05% <0.00%> (-2.95%)	⬇️
...eb-components/src/components/help-text/HelpText.ts	98.33% <0.00%> (-1.67%)	⬇️
web-components/src/components/menu/MenuItem.ts	97.50% <0.00%> (-1.25%)	⬇️
...nts/src/components/table-advanced/TableAdvanced.ts	88.26% <0.00%> (-0.49%)	⬇️
web-components/src/mixins/RovingTabIndexMixin.ts	97.27% <0.00%> (+3.63%)	⬆️
...mponents/src/components/draggable/DraggableItem.ts	100.00% <0.00%> (+6.25%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 7c48652...7986812. Read the comment docs.