eslint-plugin-wpcalypso: potential improvement for import-docblock

[jeherve]

Steps to reproduce

1. Starting on a codebase using wpcalypso/react
2. In a new file, add the following:

/**
 * WordPress dependencies
 */
import { __ } from '@wordpress/i18n';

export default {
...

3. This triggers wpcalypso/import-docblock, even though there are no other imports in the file, so we cannot have external or internal import docblocks (or they'd be empty).

I think it would make sense to update the rule to have it look for "WordPress dependencies" as well, since those can now be valid imports, on their own within a file.

Related discussion:
Automattic/jetpack#16545 (comment)