Documentation updates:

- Added a section on preventing slip in the modeling chapter.
- Added more intuitive descriptions of friction coefficients in the Computation chapter.
- Fixed some en-dashes and em-dashes.

PiperOrigin-RevId: 630856003
Change-Id: I8e767e6c5a95affdeb72ef9bc424bdd18f58e4df

doc/XMLreference.rst

@@ -301,8 +301,8 @@ adjust it properly through the XML.
    setting of solimp determines a single impedance value for all contact dimensions, which is then modulated by this
    attribute. Settings larger than 1 cause friction forces to be "harder" than normal forces, having the general effect
    of preventing slip, without increasing the actual friction coefficient. For pyramidal friction cones the situation is
-   more complex because the pyramidal approximation mixes normal and frictional dimensions within each basis vector; but
-   the overall effect of this attribute is qualitatively similar.
+   more complex because the pyramidal approximation mixes normal and frictional dimensions within each basis vector; it
+   is not recommended to use high impratio values with pyramidal cones.
 
 .. _option-gravity:
 
@@ -2274,7 +2274,8 @@ helps clarify the role of bodies and geoms in MuJoCo.
    along both axes of the tangent plane. The second number is the torsional friction, acting around the contact normal.
    The third number is the rolling friction, acting around both axes of the tangent plane. The friction parameters for
    the contact pair are combined depending on the solmix and priority attributes, as explained in :ref:`Contact
-   parameters <CContact>`.
+   parameters <CContact>`. See the general :ref:`Contact<coContact>` section for descriptions of the semantics of this
+   attribute.
 
 .. _body-geom-mass: