Suggestion: volta should use the `directory` field of the `repository` key in `package.json` to determine root config in monorepos

[runspired]

This prevents needing to have unique volta configs or re-exports in every package.json file, as long as the package.json file is correctly using the spec for specifying respository volta can easily and safely determine where the root is.

cc @chriskrycho

[Royston-Shufflebotham-i2]

Btw, you can use monorepos right now without duplicating volta configuration by adding

 "volta": {
    "extends": "../../package.json"
  }

to each child package package.json file. (You might need to adjust the path depending on the layout of your monorepo.)

[runspired]

@Royston-Shufflebotham-i2 I'm aware (hence noting it in the description). I brought up with @chriskrycho thar Volta doesn't need to do this since there's a spec it can follow instead, but it was a private convo months ago and I didn't want the knowledge to get forgotten.