fix: high contrast support

[coryrylan]

PR Checklist

Please check if your PR fulfills the following requirements:

• [ ] Tests for the changes have been added (for bug fixes / features)
• [ ] Docs have been added / updated (for bug fixes / features)
• [ ] If applicable, have a visual design approval

PR Type

What kind of change does this PR introduce?

• [x] Bugfix
• [ ] Feature
• [ ] Code style update (formatting, local variables)
• [ ] Refactoring (no functional changes, no api changes)
• [ ] Build related changes
• [ ] CI related changes
• [ ] Documentation content changes
• [ ] clarity.design website / infrastructure changes
• [ ] Other... Please describe:

What is the current behavior?

Fixes high contrast issues with design tokens and theming. This will enable high contrast support in themes and will be backported to clr-angular v5 in a followup PR

What is the new behavior?

• fixes high contrast mode issues
• add/cleanup docs for tokens/theme

Does this PR introduce a breaking change?

• [ ] Yes
• [x] No

Other information