Add history scrubbing mechanism to simulate.

[screen capture](https://www.youtube.com/watch?v=YSvWn_poqWs)

PiperOrigin-RevId: 570676968
Change-Id: Id9a1fccc9418b851e007ddcf3fa89acd4edff3e9

doc/changelog.rst

@@ -129,13 +129,27 @@ Python bindings
 22. Fixed `#870 <https://github.com/google-deepmind/mujoco/issues/870>`__ where calling ``update_scene`` with an invalid
     camera name used the default camera.
 
+Simulate
+^^^^^^^^
+
+.. youtube:: YSvWn_poqWs
+   :align: right
+   :width: 240px
+
+23. Added **state history** mechanism to :ref:`simulate<saSimulate>` and the managed
+    :ref:`Python viewer<PyViewerManaged>`. State history can be viewed by scrubbing the History slider and (more
+    precisely) with the left and right arrow keys. See screen capture:
+
+24. The ``LOADING...`` label is now shown correctly.
+    `Contribution <https://github.com/google-deepmind/mujoco/pull/1070>`__ by
+    `Levi Burner <https://github.com/aftersomemath>`__.
+
 Bug fixes
 ^^^^^^^^^
 
-23. Fixed a bug that was causing :ref:`geom margin<body-geom-margin>` to be ignored during the construction of
+25. Fixed a bug that was causing :ref:`geom margin<body-geom-margin>` to be ignored during the construction of
     midphase collision trees.
 
-
 Version 2.3.7 (July 20, 2023)
 -----------------------------