BREAKING CHANGE: Dark mode support

[nathanyoung]

Github Issue or Trello Card

This PR addresses this issue:

What type of change is this?

Please delete options that are not relevant.

• [ ] 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 not work as expected)
• [ ] Updating documentation.
• [ ] Updating deployment/build pipeline.
• [ ] Updating Project Dependencies
• [ ] Improving or adding to Test Coverage

Completeness Checklist

• [ ] TESTS: My changes maintain the baseline required test coverage, as specified by code climate analysis.
• [ ] DOCS: All new component work is covered in that component's Overview docs.
• [ ] DOCS: All new component work is covered in a component Playground.
• [ ] DOCS: All new visual changes or options are covered under relevant components' VisualTests.
• [ ] My code has no linting or typescript compile warnings.
• [ ] My work is tied to a Github issue and satisfies the acceptance criteria (if applicable) of the corresponding issue.

Quality Checklist:

• [ ] My code follows the style guidelines of this project
• [ ] I have performed a self-review of my own code
• [ ] I have commented my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation
• [ ] My changes generate no new warnings
• [ ] I have added tests that prove my fix is effective or that my feature works
• [ ] New and existing unit tests pass locally with my changes

UI Checklist

• [ ] I have conducted visual UAT on my changes/features.
• [ ] My solution works well on desktop, tablet, and mobile browsers.