Improve pipeline documentation, expose mj_implicit function to public header.

PiperOrigin-RevId: 586380774
Change-Id: I3fafa563ebc852e17e1233288455b96f4499027b

doc/APIreference/functions.rst

@@ -583,6 +583,17 @@ mj_RungeKutta
 
 Runge-Kutta explicit order-N integrator.
 
+.. _mj_implicit:
+
+mj_implicit
+~~~~~~~~~~~
+
+.. mujoco-include:: mj_implicit
+
+Integrates the simulation state using an implicit-in-velocity integrator (either "implicit" or "implicitfast", see
+:ref:`Numerical Integration<geIntegration>`), and advances simulation time. See `mjdata.h
+<https://github.com/google-deepmind/mujoco/blob/main/include/mujoco/mjdata.h>`__ for fields computed by this function.
+
 .. _mj_invPosition:
 
 mj_invPosition

doc/APIreference/functions_override.rst

@@ -69,6 +69,12 @@ These functions can be used to print various quantities to the screen for debugg
 These are components of the simulation pipeline, called internally from :ref:`mj_step`, :ref:`mj_forward` and
 :ref:`mj_inverse`. It is unlikely that the user will need to call them.
 
+.. _mj_implicit:
+
+Integrates the simulation state using an implicit-in-velocity integrator (either "implicit" or "implicitfast", see
+:ref:`Numerical Integration<geIntegration>`), and advances simulation time. See `mjdata.h
+<https://github.com/google-deepmind/mujoco/blob/main/include/mujoco/mjdata.h>`__ for fields computed by this function.
+
 .. _Subcomponents:
 
 These are sub-components of the simulation pipeline, called internally from the components above. It is very unlikely