Refine wording of page & collection privacy using password is a shared password and should not be used for secure content (Rohit Sharma, Jake Howard)
Add RelatedObjectsColumn to the table UI framework (Matt Westcott)
Reduce memory usage when rebuilding search indexes (Jake Howard)
Support creating images in .ico format (Jake Howard)
Add the ability to disable the usage of a shared password for enhanced security for the private pages and collections (documents) feature (Salvo Polizzi, Jake Howard)
Add system checks to ensure that WAGTAIL_DATE_FORMAT, WAGTAIL_DATETIME_FORMAT, WAGTAIL_TIME_FORMAT are correctly configured (Rohit Sharma, Coen van der Kamp)
Bug fixes
Fix typo in __str__ for MySQL search index (Jake Howard)
Ensure that unit tests correctly check for migrations in all core Wagtail apps (Matt Westcott)
Correctly handle date objects on human_readable_date template tag (Jhonatan Lopes)
Ensure re-ordering buttons work correctly when using a nested InlinePanel (Adrien Hamraoui)
Resolve inconsistent use of model verbose_name in group edit view when listing custom permissions (Neeraj Yetheendran, Omkar Jadhav)
Documentation
Add contributing development documentation on how to work with a fork of Wagtail (Nix Asteri, Dan Braghis)
Make sure the settings panel is listed in tabbed interface examples (Tibor Leupold)
Update content and page names to their US spelling instead of UK spelling (Victoria Poromon)
Maintenance
Move RichText HTML whitelist parser to use the faster, built in html.parser (Jake Howard)
Remove duplicate 'path' in default_exclude_fields_in_copy (Ramchandra Shahi Thakuri)
Update unit tests to always use the faster, built in html.parser & remove html5lib dependency (Jake Howard)
Adjust Eslint rules for TypeScript files (Karthik Ayangar)
Rename the React Button that only renders links (a element) to Link and remove unused prop & behavior that was non-compliant for aria role usage (Advik Kabra)
Set up an wagtail.models.AbstractWorkflow model to support future customisations around workflows (Hossein)
Improve classnames template tag to handle nested lists of strings, use template tag for admin body element (LB (Ben) Johnston)
Merge UploadedDocument and UploadedImage into new UploadedFile model for easier shared code usage (Advik Kabra, Karl Hobley)