Check for depedencies

I think with the PRs it is likely that there is going to need to be some lock files needed. I seemed to have missed this. Got this error:

`Dependencies lock file is not found in /home/runner/work/whisper-slides/whisper-slides. Supported file patterns: package-lock.json,npm-shrinkwrap.json,yarn.lock`

Perhaps this needs to be called out more loudly in the documentation? Maybe there's a script that could be run to check that things are ready for the accessibility-scanner? Not sure.

Maybe just better error messages?

Start by reviewing the documentation and dependency-checking or error-handling entry points related to the reported missing-lock-file message. The issue does not name files or tests and leaves the desired change open between documentation, a readiness script, and a better error message; done requires deciding and verifying one of those directions against the reported error.

Written by the indexing model from the issue text.