This improves page responsiveness on first load, especially on pages with many images (eg images list in Wagtail admin)
* Lazy load thumbnails on modeladmin lists
* Update oembed photos to use lazy loading
* Use lazy loading for `MediaBlock`, the avatar in the sidebar and comments
* Just decode chooser images async
- Allow users to override the default attributes given to an image
- Update tests to account for new tags
- Add documentation for custom image attributes
- Recommend that loading=lazy & decoding=async be considered for performance in front-end sites
- formatting fix for the header on small devices
- ensure the padding left is not set so that the outside is fully clickable
- fixed close button colours
- fix alignment and heights of smaller breakpoint modal header
- fixes #9053
- fixes #9014
Fixes #9010. `wagtail.documents.widgets` is no longer reliably imported on startup now that the chooser widget is constructed within wagtail.documents.views.chooser instead, so the telepath adapter wasn't getting register. This meant that DocumentChooserBlocks in StreamField were using the base chooser implementation, which didn't include customisations such as populating the title field from the file upload field. Fix this by making ChooserViewSet responsible for registering the telepath adapter.
Fixes #8989. The previous fix #9004 failed for custom document models because ChooserViewset assigns an internal name for the ChooserBlock class based on the model name, and if this is anything other than Document it won't match the name DocumentChooserBlock that it's exposed under in wagtail.documents.blocks. Fix this by replacing the `block_class` property with a `get_block_class` method that lets us specify the class name. As a bonus, user code that defines chooser blocks no longer has to directly hack the `__module__` attribute.
- fix some broken refs that were lost in the migration to markdown files
- use lower_snake_case for all internal refs (most follow this convention)
- release process sub-section in docs should be named release schedule instead
- Use inline code for `Locale` and `TranslatableMixin` headers to be consistent with other classes in the page
- Move `locale` and `translation_key` of `TranslatableMixin` to its own "Database fields" section
- Add missing periods in Page.update_aliases parameter description
Fixes #8989. Now that DocumentChooserBlock is constructed dynamically via wagtail.documents.viewsets.chooser, we need to explicitly set its `__module__` attribute so that the result of calling `deconstruct()` for migrations points back to the wagtail.documents.blocks module.
Also update the documentation for defining custom choosers, and add tests for deconstructing the other chooser blocks.
