feat: add optional node and npm dependency caching

[sd2k]

Similar to #181 but for node and npm. This has to be manually enabled
because we don't know the user's package manager.

[xnyo]

Great work! 🙌 I think this looks good and can be merged, but would love an opinion from @jackw, as he was looking into adding a shared action to detect the package manager being used in a plugin's repo.

Once that's introduced, we can make the two arguments optional and, when they're not provided, the package manager will be auto-detected. However we probably still need an input to disable caching if necessary.

I think we can merge this for now, but we may have to change/deprecate some inputs in the future. @jackw wdyt? maybe we should wait until we can auto-detect the package manager?

[tolzhabayev]

fixes #194

[tolzhabayev]

do we know what happens when those inputs are empty strings?

[sd2k]

Empty string is the default so it should work fine.

[sd2k]

I just noticed we already have a package-manager input so we could just use that...

[sd2k]

I've updated this to remove the node-cache input, which expected the package manager name, and use the existing package-manager input instead. Now the only new thing in the external ci/cd.yml files is the optional node-cache-dependency-path input which should take package.lock, yarn.lock etc.

I imagine we use @jackw's PR to automatically populate a sensible default here but the underlying setup-node action allows more customisation (e.g. for multiple package.lock files) so I don't think it's crazy to keep this option exposed - WDYT?