Add release notes for #10657

CHANGELOG.txt

@@ -25,6 +25,8 @@ Changelog
  * Update link/document rich text tooltips for consistency with the inline toolbar (Albina Starykova)
  * Increase the contrast between the rich text / StreamField block picker and the page in dark mode (Albina Starykova)
  * Purge revisions of non-page models in `purge_revisions` command (Sage Abdullah)
+ * Add support for AVIF images (Aman Pandey)
+ * Change the default WebP quality to 80 to match AVIF (Aman Pandey)
  * Fix: Prevent choosers from failing when initial value is an unrecognised ID, e.g. when moving a page from a location where `parent_page_types` would disallow it (Dan Braghis)
  * Fix: Move comment notifications toggle to the comments side panel (Sage Abdullah)
  * Fix: Remove comment button on InlinePanel fields (Sage Abdullah)

docs/releases/5.1.md

@@ -36,13 +36,19 @@ The `boost` option on `SearchField`, to increase the ranking of search results t
 
 ### Extend Stimulus adoption
 
-As part of tackling Wagtail’s technical debt and improving [CSP compatibility]([Title](https://github.com/wagtail/wagtail/issues/1288)), we have continued extending our usage of Stimulus, based on the plans laid out in [RFC 78: Adopt Stimulus](https://github.com/wagtail/rfcs/pull/78).
+As part of tackling Wagtail’s technical debt and improving [CSP compatibility](https://github.com/wagtail/wagtail/issues/1288), we have continued extending our usage of Stimulus, based on the plans laid out in [RFC 78: Adopt Stimulus](https://github.com/wagtail/rfcs/pull/78).
 
 * Migrate Tagit initialisation to a Stimulus Controller (LB (Ben) Johnston)
 * Migrate legacy dropdown implementation to a Stimulus controller (Thibaud Colas)
 * Migrate header search behaviour to `w-swap`, a Stimulus controller (LB (Ben) Johnston)
 * Replace Bootstrap tooltips with a new `w-tooltip` Stimulus controller (LB (Ben) Johnston)
 
+### AVIF image support
+
+Images can now be uploaded and rendered in [AVIF](https://en.wikipedia.org/wiki/AVIF) format; see [image file format](image_file_formats),
+[output image format](output_image_format) and [image quality](image_quality) for further details. 
+This feature was developed by Aman Pandey with input from Dan Braghis, Thibaud Colas and Chris Adams.
+
 ### Other features
 
  * Mark calls to `md5` as not being used for secure purposes, to avoid flagging on FIPS-mode systems (Sean Kelly)
@@ -64,6 +70,7 @@ As part of tackling Wagtail’s technical debt and improving [CSP compatibility]
  * Update link/document rich text tooltips for consistency with the inline toolbar (Albina Starykova)
  * Increase the contrast between the rich text / StreamField block picker and the page in dark mode (Albina Starykova)
  * Purge revisions of non-page models in `purge_revisions` command (Sage Abdullah)
+ * Change the default WebP quality to 80 to match AVIF (Aman Pandey)
 
 ### Bug fixes