Add edge ids to flex elements in mjModel.

PiperOrigin-RevId: 675130981
Change-Id: If2ccfb268142d235273b7a50e15740f6399903b2

introspect/structs.py

@@ -918,6 +918,11 @@ STRUCTS: Mapping[str, StructDecl] = dict([
                  type=ValueType(name='int'),
                  doc='number of element vertex ids in all flexes',
              ),
+             StructFieldDecl(
+                 name='nflexelemedge',
+                 type=ValueType(name='int'),
+                 doc='number of element edge ids in all flexes',
+             ),
              StructFieldDecl(
                  name='nflexshelldata',
                  type=ValueType(name='int'),
@@ -2337,6 +2342,13 @@ STRUCTS: Mapping[str, StructDecl] = dict([
                  ),
                  doc='first element vertex id address          (nflex x 1)',
              ),
+             StructFieldDecl(
+                 name='flex_elemedgeadr',
+                 type=PointerType(
+                     inner_type=ValueType(name='int'),
+                 ),
+                 doc='first element edge id address            (nflex x 1)',
+             ),
              StructFieldDecl(
                  name='flex_shellnum',
                  type=PointerType(
@@ -2393,6 +2405,13 @@ STRUCTS: Mapping[str, StructDecl] = dict([
                  ),
                  doc='element vertex ids (dim+1 per elem)      (nflexelemdata x 1)',  # pylint: disable=line-too-long
              ),
+             StructFieldDecl(
+                 name='flex_elemedge',
+                 type=PointerType(
+                     inner_type=ValueType(name='int'),
+                 ),
+                 doc='element edge ids                         (nflexelemedge x 1)',  # pylint: disable=line-too-long
+             ),
              StructFieldDecl(
                  name='flex_elemlayer',
                  type=PointerType(