fix!: fix various 8.0.0 issues

[jpandersen87]

Summary

This PR fixes some issues with the 8.0.0 release. It also addresses the issue of focus-trap-react and jsdom by requiring users to add focus-trap-react as a dependency to their projects with documentation on the issue so that they can ensure unit tests rendering Modal do not fail.

• add css files to package.json exports (credit to mdmower-csnw)
• add jest-dom to tsconfig types
• add focus-trap-react as peer dependency and exclude from library bundle
• update documentation to explain the focus-trap-react issue and to install focus-trap-react with react-uswds
• update dependencies
• updates and fixes presented yarn version (fixes errors when adding library via git)
• adds some protection against undefined properties in dangerfile

Related Issues or PRs

• 2807

How To Test

• Use this branch for the version of react-uswds in your project
• Verify that you can successfully import the index.css and uswds.css files in code
• Verify that you can mock the focus-trap-react library to prevent errors when rendering Modal in unit tests

[jpandersen87]

Temporarily moving to draft to fix git history

[jpandersen87]

Rebased off of @mdmower-csnw 's css branch to ensure he is credited.