Add `eslintConfig` to `PackageJson` type

[pting-me]

ESLint allows their configuration to be stored within the package.json. Seeing as TypeScript and Yarn configs are added, I think ESLint deserves a spot there as well.

[sindresorhus]

We cannot possible support every config that can be put into package.json. We support TypeScript as it's only 3 fields and very popular. So not sure about this one.

[sindresorhus]

Do you actually need this or are did you just notice it was missing?

[voxpelli]

I agree with @sindresorhus, at most it would be as part of something like PackageJsonExtras, but also nothing stopping eg ESLint themselves to publish a type for their property, which would be even better than us maintaining it here 👍

Have you tried asking the ESLint project? If they reject the idea, then we can revisit it here?

[pting-me]

Yeah I actually do need this for another project. I've done my own implementation for the time being.

There is a definition in @types/eslint for their configuration object: Linter.Config. I'm proposing that the PackageJson include a property eslintConfig that points to that type. I just noticed you don't have any dependencies on other @types packages, so wanted to check in if that was a specific design decision. Otherwise, the change should be fairly simple, and I can raise a PR.

@voxpelli makes a good point about having some sort of PackageJsonExtras. Perhaps we should consider that for other possible package.json additions (including this one). Thoughts?

[voxpelli]

Added comment to #372, lets keep the discussion there then