USWDS-Site - Refresh resources linked on Design Principles page

[brunerae]

Is your feature request related to a problem? Please describe.

Resources linked throughout the Design Principles page are aging or no longer relevant.

Describe the solution you'd like

We should review links on the page to find fresher content.

Describe alternatives you've considered

No response

Additional context

No response

Code of Conduct

• [X] I agree to follow this project's Code of Conduct.
• [X] I checked the current issues for duplicate feature requests.

[annepetersen]

We will need to include this issue on the TTS audit until it’s resolved

[finekatie]

Created additional issue to audit the links: Audit links on Design principles page #2733