FITB: Dynamic substitutions require node modules be installed.

[dbrianwalton]

I believe that this captures the CLI requirements to match pretext PR #2577. Before the dynamic substitution extraction routine in core can be called, we need to ensure that the associated node packages are installed. (In pretext/script/dynsub). Node can't load the dynamic JS libraries that Runestone components require for versions below 22.10, and which is required to generate the randomized content that is being extracted.

I made three key changes mimicking what was happening with themes (also require npm install), but don't know how to test them:

1. Update the install script to install script/dynsub node packages
2. Add a test routine (ensure_dynsub_node_packages) which tries to install if missing
3. Update the routine that calls core:dynamic_substitutions to call the test routine

I don't know of any other changes that would be required. This is more intended to point out what I understand would be needed, and I hope it is enough for you to understand if anything else is missing.

[oscarlevin]

Thanks. I edited one of the error messages and updated the core commit to make sure it had the most recent changes. Worked well.