Instead of using a bundled node_modules,
* If `npm` isn't available (e.g. in a container), install it
* Run `npm install` before performing various tasks

Change pr-checks to not be particularly picky about the generated
content because it will differ between different versions as everything
is bundled together.

For review, the deletion of node_modules and lib will be in a distinct
commit.

This reduces the cost to download repository as an action.

This commit is logically part of the previous commit, but is split to
enable the preceding commit to be reviewed.