doc: update changelog

Author: aleneum

Changelog.md

@@ -6,6 +6,7 @@
 - PR #696: Improve handling of `StrEnum` which were previously confused as string (thanks @jbrocher)
 - Bug #697: An empty string as a destination made a transition internal but only `dest=None` should do this (thanks @rudy-lath-vizio)
 - Bug #704: `AsyncMachine` processed all `CancelledErrors` but will from now on only do so if the error message is equal to `asyncio.CANCELLED_MSG`; this should make bypassing catch clauses easier; requires Python 3.11+ (thanks @Salier13)
+- Feature #710: `experimental.utils.generate_base_model` can now be called with an instance of MarkupMachine directly (thanks @patrickwolf)
 
 ## 0.9.3 (July 2024)