Add missing face attribute to the XML schema.

PiperOrigin-RevId: 561330536
Change-Id: I693fc5228591e4a26ea0749435a6ce9869afd457

src/xml/xml_native_reader.cc

@@ -270,8 +270,8 @@ static const char* MJCF[nMJCF][mjXATTRNUM] = {
         {"light", "*", "15", "name", "class", "directional", "castshadow", "active",
             "pos", "dir", "attenuation", "cutoff", "exponent", "ambient", "diffuse", "specular",
             "mode", "target"},
-        {"composite", "*", "12", "prefix", "type", "count", "spacing", "offset",
-            "flatinertia", "solrefsmooth", "solimpsmooth", "vertex",
+        {"composite", "*", "13", "prefix", "type", "count", "spacing", "offset",
+            "flatinertia", "solrefsmooth", "solimpsmooth", "vertex", "face",
             "initial", "curve", "size"},
         {"<"},
             {"plugin", "*", "2", "plugin", "instance"},
@@ -1943,6 +1943,9 @@ void mjXReader::OneComposite(XMLElement* elem, mjCBody* pbody, mjCDef* def) {
     String2Vector(text, comp.uservert);
   }
 
+  // shell
+  ReadAttrTxt(elem, "face", comp.userface);
+
   // process curve string
   std::istringstream iss(curves);
   int i = 0;