Watch `exclude` files if they are dependencies

[fwkoch]

Currently exclude in the project config does 2 things:

• prevents those files from getting added to the implicit project toc
• prevents those files from being watched during myst start

However, there is a very realistic case where a dependency (e.g. a notebook that generates a figure used in another markdown page) needs to be excluded from the implicit toc but still watched for changes, so the dependent pages update.

I don't think this needs any configuration, we simply remove dependencies from chokidar.watch's ignored patterns.