Add npm command to run deadlink checker (from quarto-publish workflow)

[maehr]

Describe what feature you'd like. Pseudo-code, mockups, or screenshots of similar solutions are encouraged!

Please add an npm script/command to package.json that allows maintainers to run the deadlink checker locally, as defined in the .github/workflows/quarto-publish.yml workflow. This should make it easy to check for broken links before pushing or as part of local development.

Suggested steps:

• Review the deadlink checking logic in the workflow (deadlinkcheck job and related steps).
• Add a corresponding npm script (e.g., npm run deadlink-check) that runs the same logic/tools as the workflow.
• Document this new command in the README.

This will help ensure link quality and parity between CI and local development environments.

What type of pull request would this be?

Enhancement

Any links to similar examples or other references we should review?

The deadlink checker is set up in the workflow: https://github.com/maehr/open-research-data-template/blob/main/.github/workflows/quarto-publish.yml