Add mjs_attachFrameToSite.

This is required in preparation of changing the spec.attach behavior in the Python bindings.

PiperOrigin-RevId: 730810198
Change-Id: I095808f0afe62b5bbd27201ed5c75804e0e9c4bf

doc/APIreference/functions.rst

@@ -3836,6 +3836,15 @@ Attach child frame to a parent body, return the attached frame if success or NUL
 
 Attach child body to a parent site, return the attached body if success or NULL otherwise.
 
+.. _mjs_attachFrameToSite:
+
+`mjs_attachFrameToSite <#mjs_attachFrameToSite>`__
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. mujoco-include:: mjs_attachFrameToSite
+
+Attach child frame to a parent site, return the attached frame if success or NULL otherwise.
+
 .. _mjs_detachBody:
 
 `mjs_detachBody <#mjs_detachBody>`__

doc/includes/references.h

@@ -3602,6 +3602,8 @@ mjsFrame* mjs_attachFrame(mjsBody* parent, const mjsFrame* child,
                           const char* prefix, const char* suffix);
 mjsBody* mjs_attachToSite(mjsSite* parent, const mjsBody* child,
                           const char* prefix, const char* suffix);
+mjsFrame* mjs_attachFrameToSite(mjsSite* parent, const mjsFrame* child,
+                                const char* prefix, const char* suffix);
 int mjs_detachBody(mjSpec* s, mjsBody* b);
 mjsBody* mjs_addBody(mjsBody* body, const mjsDefault* def);
 mjsSite* mjs_addSite(mjsBody* body, const mjsDefault* def);