4.0 release notes - pull out documentation updates

- include a relevant summary of the Wagtail Sphinx theme updates
- relates to #9013

docs/releases/4.0.md

@@ -104,11 +104,23 @@ The bulk of these enhancements have been from Paarth Agarwal, who has been doing
    * Adopt the slim header in page listing views, with buttons moved under the "Actions" dropdown
    * Add convenient access to the translate page button in the parent "more" button
 
+### Documentation improvements
+
+The documentation now has dark mode which will be turned on by default if set in your browser or OS preferences, it can also be toggled on and off manually. The colours and fonts of the documentation now align with the design updates introduced in Wagtail 3.0. These features were developed by Vince Salvino.
+
+There are also many improvements to the documentation both under the hood and in the layout;
+
+ * Convert the rest of the documentation to Markdown, in place of RST, which will make it much easier for others to contribute to better documentation (Khanh Hoang, Vu Pham, Daniel Kirkham, LB (Ben) Johnston, Thiago Costa de Souza, Benedict Faw, Noble Mittal, Sævar Öfjörð Magnússon, Sandeep M A, Stefano Silvestri)
+ * Replace latin abbreviations (i.e. / e.g.) with common English phrases so that documentation is easier to understand (Dominik Lech)
+ * Improve organisation of the settings reference page with logical grouping and better internal linking (Akash Kumar Sen)
+ * Improve the accessibility of the documentation with higher contrast colours, consistent focus outline, better keyboard only navigation through the sidebar (LB (Ben) Johnston, Vince Salvino)
+ * Better sidebar scrolling behaviour, it is now sticky on larger devices and scrollable on its own (Paarth Agarwal, LB (Ben) Johnston)
+ * Fix links showing incorrectly in Safari (Tibor Leupold)
+ * See other features below for new feature specific documentation added.
 
 ### Other features
 
  * Add clarity to confirmation when being asked to convert an external link to an internal one (Thijs Kramer)
- * Convert the rest of the documentation to Markdown (Khanh Hoang, Vu Pham, Daniel Kirkham, LB (Ben) Johnston, Thiago Costa de Souza, Benedict Faw, Noble Mittal, Sævar Öfjörð Magnússon, Sandeep M A, Stefano Silvestri)
  * Add `base_url_path` to `ModelAdmin` so that the default URL structure of app_label/model_name can be overridden (Vu Pham, Khanh Hoang)
  * Add `full_url` to the API output of `ImageRenditionField` (Paarth Agarwal)
  * Use `InlinePanel`'s label when available for field comparison label (Sandil Ranasinghe)
@@ -156,13 +168,11 @@ The bulk of these enhancements have been from Paarth Agarwal, who has been doing
  * Use new modal dialog component for privacy settings modal (Sage Abdullah)
  * Add `menu_item_name` to modify `MenuItem`'s name for `ModelAdmin` (Alexander Rogovskyy, Vu Pham)
  * Add an extra confirmation prompt when deleting pages with a large number of child pages, see [](wagtailadmin_unsafe_page_deletion_limit) (Jaspreet Singh)
- * Replace latin abbreviations (i.e. / e.g.) with common English phrases so that documentation is easier to understand (Dominik Lech)
  * Add shortcut for accessing StreamField blocks by block name with new [`blocks_by_name` and `first_block_by_name` methods on `StreamValue`](streamfield_retrieving_blocks_by_name) (Tidiane Dia, Matt Westcott)
  * Add HTML-aware max_length validation and character count on RichTextField and RichTextBlock (Matt Westcott, Thibaud Colas)
  * Remove `is_parent` kwarg in various page button hooks as this approach is no longer required (Paarth Agarwal)
  * Improve security of redirect imports by adding a file hash (signature) check for so that any tampering of file contents between requests will throw a `BadSignature` error (Jaap Roes)
  * Allow generic chooser viewsets to support non-model data such as an API endpoint (Matt Wescott)
- * Improve organisation of the settings reference page in the documentation (Akash Kumar Sen)
  * Added `path` and `re_path` decorators to the `RoutablePageMixin` module which emulate their Django URL utils equivalent, redirect `re_path` to the original `route` decorator (Tidiane Dia)
  * `BaseChooser` widget now provides a Telepath adapter that's directly usable for any subclasses that use the chooser widget and modal JS as-is with no customisations (Matt Westcott)
  * Introduce new template fragment and block level enclosure tags for easier template composition (Thibaud Colas)