Create documentation page for the module Link

As pointed out in #1892548: Official documentation pages missing for new Drupal 8 Modules documentation is missing for new core modules among them Link.

Tasks:

1. Create docs page for module under url http://drupal.org/documentation/modules/link
2. Notify maintainer(s) & request technical review
3. Notify technical authors and request style review
4. (If a project page exists) Ask for a link from project page
5. Review if correctly placed in docs outline
6. Reference to docs on project page