[Feature] Add useTheme hook. Update Link and Alert to use themes

[narin]

Description of Change

• Imports new themes from tokens package
• Update all instances of Colors to renamed colors
• Adds useTheme() hook which checks for light/dark mode from useColorScheme() and returns the appropriate theme
• Updates Link and Alert components to use themes
• Ticket to update remainder of the components: https://github.com/department-of-veterans-affairs/va-mobile-library/issues/371

Testing Packages

N/A

Screenshots/Video

Link

Before/After

Before/After (Dark Mode)

Alert

Info Before/After

Info Before/After (Dark Mode)

Warning Before/After

Warning Before/After (Dark Mode)

Error Before/After

Error Before/After (Dark Mode)

Testing

• [ ] Tested on iOS
• [ ] Tested on Android
• [ ] Tested on Web

PR Checklist

Code reviewer validation:

• General
  • [x] PR is linked to ticket(s)
  • [x] PR has changelog label applied if it's to be included in the changelog
  • [x] Acceptance criteria:
    • All satisfied or
    • Documented reason for not being performed or
    • Split to separate ticket and ticket is linked by relevant AC(s)
  • [x] Above PR sections adequately filled out
  • [x] If any breaking changes, in accordance with the pre-1.0.0 versioning guidelines: a CU ticket has been created for the VA Mobile App detailing necessary adjustments with the package version that will be published by this ticket
• Code
  • [x] Tests are included if appropriate (or split to separate ticket)
  • [x] New functions have proper TSDoc annotations

Publish

If changes warrant a new version per the versioning guidelines and the PR is approved and ready to merge:

• [ ] Merge main into branch
• [ ] Merge branch to main
• [ ] Verify that Check Component Integrations workflow ran successfully
• [ ] Publish new version after merging