Changes from 3.0rc2:

• Design review fixes
• Added API documentation for panels
• Hide 'More actions' dropdown when bulk actions are active
• Defer making use_json_field argument on StreamField required until Wagtail 5.0
• Document requirement for Sqlite JSON1 extension
• Remove is_searchable check from shared header template
• Ensure wagtail updatemodulepaths works when system locale is not UTC