No internal module export

[adjerbetian]

Proposition

Make the rule no-internal-modules also prevent exporting the submodules of other modules.
(currently it only prevents importing)

Description of the problem

When no-internal-modules is set to error, here is what we have:

import { f } from "./modules/submodule"  // error
export { f } from "./modules/submodule"  // no error

This is annoying because it breaks the idea that a folder decides what it makes available to the exterior, and therefore, everything is accessible.

Example

For instance, one could have

module1/
    private/
        f.js
module2/
    hacked_f.js
    g.js

with

//hacked_f.js
export { f } from "../module1/private/f"

//g.js
import { f } from "./hacked_f.js"

[ljharb]

This seems like a good thing to add - although it would have to be behind an option to avoid being semver-major.