[Feature Request] Support Node versions <14

[Alonski]

Currently, the engines property in the package.json is set to >14
This means that Node versions v12, for example, don't work.

https://github.com/jelhan/create-github-actions-setup-for-ember-addon/blob/master/package.json#L49

To get around this I switched to Node version v14 using NVM.