docs: add event humanized name to 3.1.0 release notes

Author: fgmacedo

docs/releases/3.1.0.md

@@ -158,4 +158,11 @@ machine instance concurrently. This is now documented in the
   interpreted as the event `id`, leaving the extra transitions eventless (auto-firing).
   [#588](https://github.com/fgmacedo/python-statemachine/pull/588).
 
+- `Event.name` is now auto-humanized from the `id` (e.g., `cycle` → `Cycle`,
+  `pick_up` → `Pick up`). Diagrams, Mermaid output, and text tables all display
+  the human-readable name. Explicit `name=` values are preserved. The same
+  `humanize_id()` helper is now shared by `Event` and `State`.
+  [#601](https://github.com/fgmacedo/python-statemachine/pull/601),
+  fixes [#600](https://github.com/fgmacedo/python-statemachine/issues/600).
+
 ## Misc in 3.1.0