[Task]: Markdown link checker

[daphnegold]

Summary

Let's check for broken links! Suggest we use a tool implemented into Github Actions pipeline from marketplace

Example: https://github.com/usds/justice40-tool/blob/c7dd4f20d7e930e734aab3c4f143a396a3f586e6/.github/workflows/markdown-link-check.yml#L4

Acceptance criteria

• [ ] Integrate markdown link check tool
• [ ] Update associated ADRs #102 #101

[acouch]

I tested linkcheckmd, and it is not fully functional.

I had success with markdown-link-check. It has pre-commit integration, so worth trying.

[acouch]

We can pick up the implementation here! https://github.com/navapbc/template-infra/pull/497