List ESLint and plugins as peerDependencies + use babel-eslint parser

[fnwbr]

Sorry - this is some back and forth after #7.
But when I was trying to install the update to our Web-Expensify repository I noticed that ESLint does not scan subdirectories of node_modules/ for plugins anymore.

So it is not enough to list e.g. eslint-plugin-react as a dependency of this package anymore, but we need to actually install it as a separate first-level dependency in Web-Expensify.

To do so properly, you'd mention them here as peerDependency.

Extra note: ESLint is working on undoing that at some point again, the RFC proposal was accepted already: eslint/rfcs#7
But the actual implementation is still pending: eslint/rfcs#14

And I don't really want to hold on that now.

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Second thing: We need to use babel-eslint as our parser, because (for whatever reason) ESLint seems to have dropped the support to do React out of the box. I couldn't really find the changelog item pointing that out, but with this change everything is working again. Allegedly it has always been like that, but that made me wonder how it has worked in the past for us. Let me know if you have other ideas, but we acn also just merge this as is.

[objectsforheads]

🌮

[arimai]

why this?

[fnwbr]

This is saying: When linting this repository (eslint-config-expensify) we lint it with the ruleset of the "legacy" rules. And since we only write plain vanilla JavaScript, I figured that's alright. We don't need plugins like eslint-plugin-react or eslint-plugin-jsx-a11y here.

[arimai]

Second thing: We need to use babel-eslint as our parser, because (for whatever reason) ESLint seems to have dropped the support to do React out of the box.

I am confused by this, like you also mentioned, eslint never supported react out of the box, thats why we use eslint-plugin-react no?
And babel-eslint AFAIK is for experimental ES features, not sure why we need that to make this work 🤔