chore: warn when node 12+ isn't used

[pandu-supriyono]

Added a node script in the project root directory as opposed to creating a bin/scripts directory since there aren't any scripts of similar nature around (yet).

Closes issue: #3544

[CLAassistant]

All committers have signed the CLA.

[pandu-supriyono]

@stephenmathieson thanks for having a look and the feedback! I can see to it again tomorrow.

One last request as I'd appreciate thoughts on the following:

Using an .nvmrc is a good idea -- in that case we could dynamically load that file into the check-node-version script and assign it to minimumVersion.

In my view, this would make maintenance easier since it constrains the source of truth with regards to the minimum node version to the .nvmrc file (excluding the docs).

[straker]

@pandu-supriyono Let's go ahead and drop the .nvmrc file so we don't force users to use an older version of node. If you remove the file and revert the changes to the script to use the .nvmrc file, I think this should be good to merge.

Thanks again for working on this

[pandu-supriyono]

@straker Got it -- done in 387c3fc

Thanks again 😃

[straker]

Apologies on the back-and-forth trying to figure out the .nvmrc file. Do you think you'll have some time this week to address https://github.com/dequelabs/axe-core/pull/3580#pullrequestreview-1072878912?

[WilcoFiers]

Oh, right! Reviewed for security.