Eslint: add support for class properties

[marcofugaro]

Related issue: #20009 (comment)

Description

Eslint also needs to know about babel to support class properties.
In this PR I added @babel/eslint-parser as a parser for eslint. This does not change the current eslint bahaviour.

I also put the babelrc in a custom file babel.config.js because it's needed for eslint and removed an unused String.prototype.replaceAll()

[Mugen87]

Related: #21170 (comment)

[mrdoob]

Thanks!

[mrdoob]

This broke ESLint for me:

I tried doing npm update and npm install.

[mrdoob]

This is blocking me. I'll have to revert.

[marcofugaro]

@mrdoob is that your editor? What happens if you do npm run lint-fix? On my machine it runs eslint just fine

[mrdoob]

Yep, it's Atom. I'll try later tonight.

[marcofugaro]

Okay, I'll do a new configuration which doesn't involve that ./utils/build/babel.config.json path thing, let me know if that works for you when you'll try it later!

Edit: done!