minor #748 [Live] Adding missing versionadded for smart re-rendering system (weaverryan)

This PR was merged into the 2.x branch.

Discussion
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[Live] Adding missing versionadded for smart re-rendering system

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| Tickets       | From a comment on Slack
| License       | MIT

`versionadded` was missing, which is especially important since this feature is not released yet.

Commits
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4e026d0e [Live] Adding missing versionadded for smart re-rendering system

Author: fullstackdeveloperwebapp

src/LiveComponent/doc/index.rst

@@ -2214,6 +2214,10 @@ When a component re-renders, the new HTML if "morphed" onto the existing
 elements on the page. For example, if the re-render includes a new ``class``
 on an existing element, that class will be added to that element.
 
+.. versionadded:: 2.8
+
+    The smart re-render algorithm was introduced in LiveComponent 2.8.
+
 The rendering system is also smart enough to know when an element was changed
 by something *outside* of the LiveComponents system: e.g. some JavaScript
 that added a class to an element. In this case, the class will be preserved