Support and test Maintenence and LTS versions of Node.js

[flevi29]

https://github.com/nodejs/Release
There are a few issues that this will unblock/make easier and saner to implement:

• Update ESLint, Prettier, TypeScript and fix/improve their configuration files #1616
  • latest @typescript-eslint/eslint-plugin doesn't support Node.js 14 anymore
• problematic tests regarding Node.js built-in fetch #1612 and UMD bundled version theoretically should err on browsers without native fetch support #1610
  • all Node.js versions under active development and maintenance have builtin fetch, so as to not have to test for different implementations of fetch (namely node-fetch from within cross-fetch for Node.js 14 and 16 and builtin undici fetch for Node.js 18 (cross-fetch/polyfill only works if there isn't already a fetch function globally defined)), lets switch to officially supporting 18 and 20 this no longer applies because of Update Jest #1622 disabling builtin fetch with a setup script