Compatibility with `jest`

[jackyef]

jestjs/jest#5741 (comment)

Jest has its own cache, so when running with jest, the following error is always thrown.

Could not find ESLint Linter in require cache

[Conduitry]

Is there some way to access the cache when using Jest? Because of ESLint API limitations, we do need to be able to monkeypatch some stuff on the copy of ESLint that's going to be used during the build or linting or tests or whatever.

The eventual proper way to fix this (and maybe the only way, depending on what Jest exposes) will be to get this feature implemented in ESLint, so that there's no longer a need to monkeypatch.