CKEditor5 hook_help implementation points to contrib module docs

Problem/Motivation

Two links generated by ckeditor5_help are still pointing to contrib documentation on drupal.org. Those links redirect to a page which indicates that ckeditor5 is still an experimental module. Despite the fact that it is now stable for a while. The links in question point to the following locations:

• https://www.drupal.org/docs/contributed-modules/ckeditor-5 →
• https://www.drupal.org/docs/contributed-modules/ckeditor-5/plugin-and-contrib-module-development →

However, it looks like there is already an up-to-date guide in core modules and themes documentation (at least for the first link):

• https://www.drupal.org/docs/core-modules-and-themes/core-modules/ckeditor-5-module →

Steps to reproduce

Open admin/help/ckeditor5 on a newly installed site.

Proposed resolution

1. Move missing ckeditor5 documentation guides on drupal.org to the proper location (i.e., outside the experimental modules page).
2. Add redirects on drupal.org from the old to the new location.
3. Update links in hook_help.

Remaining tasks

User interface changes

API changes

Data model changes

Release notes snippet