Add changelog & upgrade considerations for Stimulus dialog/teleport u…

…sage

- Closes wagtail#10174
- See PR wagtail#10397

docs/releases/5.1.md

@@ -38,10 +38,13 @@ The `boost` option on `SearchField`, to increase the ranking of search results t
 
 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).
 
+* Add support for `attrs` on `FieldPanel` and other panels to aid in custom Stimulus usage (Aman Pandey, Antoni Martyniuk, LB (Ben) Johnston)
 * 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)
+* Migrate dialog instantiation to a new `w-dialog` Stimulus controller (Loveth Omokaro, LB (Ben) Johnston)
+* Support dialog template cloning using a new `w-teleport` Stimulus controller (Loveth Omokaro, LB (Ben) Johnston)
 
 ### AVIF image support
 
@@ -145,6 +148,8 @@ This feature was developed by Aman Pandey as part of the Google Summer of Code p
  * Update uuid to v9 and Jest to v29, with `jest-environment-jsdom` and new snapshot format (LB (Ben) Johnston)
  * Update test cases producing undesirable console output due to missing mocks, uncaught errors, warnings (LB (Ben) Johnston)
  * Remove unused snippets _header_with_history.html template (Thibaud Colas)
+ * Migrate dialog instantiation to a new `w-dialog` Stimulus controller, including in the Userbar (Loveth Omokaro, LB (Ben) Johnston)
+ * Support dialog template cloning using a new `w-teleport` Stimulus controller (Loveth Omokaro, LB (Ben) Johnston)
 
 ## Upgrade considerations
 
@@ -343,3 +348,19 @@ The undocumented Bootstrap jQuery tooltip widget is no longer in use, you will n
 <!-- New attributes: -->
 <span data-controller="w-tooltip" data-w-tooltip-content-value="Tooltip content here">Label</span>
 ```
+
+### Dialog hide/show custom events name change
+
+The undocumented client-side Custom Event handling for dialog showing & hiding will change in a future release.
+
+| Action | Old event      | New event       |
+| ------ | -------------- | --------------- |
+| Show   | `wagtail:show` | `w-dialog:show` |
+| Hide   | `wagtail:hide` | `w-dialog:hide` |
+
+Additionally, two new events will be dispatched when the dialog visibility changes.
+
+| Action | Event name        |
+| ------ | ----------------- |
+| Show   | `w-dialog:shown`  |
+| Hide   | `w-dialog:hidden` |