Fix broken links in Markdown files

[replaceafill]

This also introduces markdown-link-check as a pre-commit hook to check broken links in the Markdown files of the repository. The hook has been set as manual to not interfere in the usual development workflow.

For example, to check links in a specific file:

pre-commit run --hook-stage manual markdown-link-check --files src/dashboard/frontend/README.md

Or to check all the Markdown files in the repository:

pre-commit run --hook-stage manual markdown-link-check --all-files

We should not include this in the pull request workflow because link checking is flaky. Sometimes working links fail from GitHub hosts because websites block them. But we could potentially create a separate workflow that developers could trigger manually.

[Dhwaniartefact]

Thanks for adding this. LGTM !