Use "exports" as alternative to "/node" and "/native" import paths

[kettanaito]

Scope

Adds a new behavior

Compatibility

• This is a breaking change

Feature description

We can utilize the exports field of package.json to automatically expose the correct exports based on the environment where msw is being imported in. This would allow us to drop import path like msw/node and msw/native, making the library more predictable across environments.

{
  "exports": {
    "./": {
      "browser": "./lib/browser/...",
      "node": "./lib/browser/..."
    }
  }
}

This is a very basic example as each export would also have to point to its own "types" so the "browser" and "node" fields must be expanded with the "type" key as well as the export type key.

It also makes sense to ship this change with backward-compatibility so people on old bundlers could still use MSW as before: via msw/node and msw/native direct imports. We may consider dropping those imports after some time.

[kettanaito]

This has been implemented in #1404.