feat: strictly define Node API in plugin template

[bmish]

This follows the lead of ESLint core and other ESLint plugins in strictly defining their Node API so that users cannot reach in and import/depend on arbitrary files inside the plugin.

• https://eslint.org/docs/latest/user-guide/migrating-to-8.0.0#remove-lib

  Beginning in v8.0.0, ESLint is strictly defining its public API. Previously, you could reach into individual files such as require("eslint/lib/rules/semi") and this is no longer allowed. There are a limited number of existing APIs that are now available through the /use-at-your-own-risk entrypoint for backwards compatibility, but these APIs are not formally supported and may break or disappear at any point in time.

https://nodejs.org/api/packages.html#main-entry-point-export

[nzakas]

This is technically a breaking change so holding off on merging until we are sure we want to do a major release.

[bmish]

@nzakas if we are considering breaking changes in the plugin template to be breaking changes for generator-eslint, then isn't #136 also a breaking change? I was unsure if plugin template changes should rise to the level of breaking changes.

[nzakas]

That's a good point. When I reviewed this last night I think I missed that it was the template package.json rather than the package package.json. So I think you're right, this shouldn't be a breaking change.