This issue is part of the task to update the hook_help texts of the Drupal 8 modules:
- Review / write the hook_help text according to help guidelines
- Refactor the enabled field modules list, using annotation-based discovery. [out of scope for this issue]
- (novice) Final manual testing:
1. Apply the patch.
2. Go to admin/help.
3. Click on the help page for this module (Field).
4. Verify that the help page is OK:
- Verify that all the links work
- Verify that all mentions of pages/text/permissions within the UI match what is seen in the UI
- Verify that the formatting is OK.
- (detail in comment 23)