This creates a monorepo for each github action and ensures they all use pnpm.
You can install and build all with the following:
```
cd .github
pnpm i
pnpm -r build
```
- Add some basic error handling to the link validator action.
- Avoid unnecessarily creating a new bot comment when the validation is successful.
- Only scan .mdx files modified in the current PR for broken links.
This PR migrates and adapts the [validate docs links script from `next-site`](https://github.com/vercel/front/pull/23185). This script is triggered by a GitHub action whenever a file in the `/docs` folder is updated. If broken links are found in the docs, the check fails and we post a comment on the PR with a list of broken links.
Co-authored-by: Michael Novotny <446260+manovotny@users.noreply.github.com>
