Color visited links distinctly

[m-akinc]

Pull Request

🤨 Rationale

Part of #2011

👩‍💻 Implementation

• Changed color of visited anchors per the design in Figma.
• Created two new theme-aware tokens for this
• Added interesting "visited" cases to the anchor's interaction matrix story. This required updates to the createMatrixInteractionsFromStates utility function.

🧪 Testing

Added visual tests, and manually tested in Storybook.

✅ Checklist

• [x] I have updated the project documentation to reflect my changes or determined no changes are needed.

[m-akinc]

@mollykreis could you please buddy for me?

[m-akinc]

Based on group discussion, we're going to hold off on coloring visited links. Since we're not sure we want this, we won't keep around a work item for it.