Drop Node.js version 12

[n1ru4l]

Node.js 12 is no longer in the Maintenance schedule. We should remove it and release a new major version.

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• https://nodejs.org/en/about/releases/
• Drop official Node.js 12 support #1417

[dimaMachina]

Don't forget to mention me to add some breaking ESLint rules, like forbid export default and change filenames ;)

[n1ru4l]

Yeah sure, it can be a separate pull request, that we can merge before releasing the PR. Can you already create a draft PR of this?

[dimaMachina]

I'll do it now