ESLINT-32 add import/no-exteneous-dependencies

[samelliottdlt]

We had a little discussion about this rule during band meeting and I've talked to @gatsbyz on the side about getting this rule up and running.

The configuration that we have here will result in all imports of packages that are not defined in the package.json will result in an error. I know there are a few services that use aws-sdk without having it as a dependency in their package.json.

Dev dependencies can only be used within .spec and .test files.

This repo doesn't have labels. I'll publish it manually after it has been merged.

[carlansley]

one wrinkle I thought of, do you know if this works with the new typescript import type syntax? it would be ok for prod code to import devDependencies in this case, i've used it a bit already. (.e.g. import type { v2 as account } from '@checkdigit/account';, where account is a devDependency)

[samelliottdlt]

@carlansley looks like the answer is no. Check out this issue: import-js/eslint-plugin-import#1618

The latest comment comments on how it fails with import/types. Looks like the solution would be to losen the dev dependency but I think that makes @gatsbyz's rollup issue possible again.

[gatsbyz]

lgtm

[carlansley]

@samelliottdlt think we can ignore this issue for now, I'm sure they'll fix it in the fullness of time. And I doubt import type is used in very many places.