Documentation improvements for 2.1.1.

- Fix typos and broken links.
- Add documentation for functions introduced in 2.1.1.
- Add copyright header to `FLV.m` and remove `hello.c`.
- Update documentation for `mj_ray` and `mj_contactForce`.
- Delete out-of-date comments in `XMLreference.rst`.
- Add geom:size table to `XMLreference.rst`.

PiperOrigin-RevId: 425318966

doc/_static/FLV.m

@@ -1,3 +1,18 @@
+% Copyright 2021 DeepMind Technologies Limited
+%
+% Licensed under the Apache License, Version 2.0 (the "License");
+% you may not use this file except in compliance with the License.
+% You may obtain a copy of the License at
+%
+%     http://www.apache.org/licenses/LICENSE-2.0
+%
+% Unless required by applicable law or agreed to in writing, software
+% distributed under the License is distributed on an "AS IS" BASIS,
+% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+% See the License for the specific language governing permissions and
+% limitations under the License.
+
+
 % Force-Length-Velocity function of MuJoCo muscle model
 % Defaults: FLV(0.5, 1.6, 1.5, 1.3, 1.2)
 

doc/_static/hello.c

@@ -1,34 +0,0 @@
-#include "mujoco.h"
-#include "stdio.h"
-
-char error[1000];
-mjModel* m;
-mjData* d;
-
-int main(void)
-{
-   // activate MuJoCo Pro
-   mj_activate("mjkey.txt");
-
-   // load model from file and check for errors
-   m = mj_loadXML("hello.xml", NULL, error, 1000);
-   if( !m )
-   {
-      printf("%s\n", error);
-      return 1;
-   }
-
-   // make data corresponding to model
-   d = mj_makeData(m);
-
-   // run simulation for 10 seconds
-   while( d->time<10 )
-      mj_step(m, d);
-
-   // free model and data, deactivate
-   mj_deleteData(d);
-   mj_deleteModel(m);
-   mj_deactivate();
-
-   return 0;
-}