eslint-plugin: peerDependency warning with eslint@7.0.0

[AviVahl]

Actual
eslint@7.0.0 has been released yesterday. @typescript-eslint/eslint-plugin gets a peerDependency warning:

npm WARN @typescript-eslint/eslint-plugin@2.31.0 requires a peer of eslint@^5.0.0 || ^6.0.0 but none is installed. You must install peer dependencies yourself.

Expected
Install without warnings when used with the latest eslint release.

Versions

package	version
@typescript-eslint/eslint-plugin	2.31.0
@typescript-eslint/parser	2.31.0
TypeScript	3.8.3
ESLint	7.0.0
node	12.6.3
npm	6.14.4

[bradzacher]

This is valid.
We don't yet support ESLint v7 - we have not tested any of our project against it.

Once we support it, we will update the dependency ranges.

#1550