[create-block] Add npmDevDependencies as a template variable.

[ryanwelcher]

What?

This PR adds a new template variable to the create-block package to allow templates to define devDependencies.

Closes #39722

Why?

Some blocks require devDependences that should not be added to regular dependencies.

How?

This is done by introducing a npmDevDependencies variable

Testing Instructions

1. Download https://github.com/ryanwelcher/dynamic-block-template and add a npmDevDependencies entry to the index.js and add an array of dependencies
   Run ./node_modules/.bin/wp-create-block --template={pathTo}/dynamic-block-template

[gziolo]

I haven't had a chance to test that yet. The changes proposed in the PR look great though 👍🏻

Any idea why CI jobs didn't start?

[ryanwelcher]

Thanks, @gziolo! Not sure about the CI either, I tried pushing another commit to restart the jobs but that did nothing.

[dgwyer]

Just updated a couple of typos.

[ryanwelcher]

For posterity, I was able to get the CI job to re-run by rebasing from trunk and force-pushing the changes as per @c4rl0sbr4v0 in WP Make slack.