Version 2.1.1: Binaries for ARM64, proper macOS bundles, minor bugfixes.

Closes #2
Closes #42
Closes #59

PiperOrigin-RevId: 416794598
Change-Id: I1306df1127d6acecf2323873c0da0910f35d31a0

model/flag/flag.xml

@@ -0,0 +1,44 @@
+<!-- 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.
+-->
+
+<mujoco model="Flag">
+<!-- Degree of Freedom (nv):  340
+     Tendons (ntendon):       288
+     Actuators (nu):          0
+     Constraints (nefc):      0
+     This model of a flag passively flapping in the wind has no constraints and is designed to
+     exert smooth dynamics computations.
+-->
+  <statistic center=".4 0 .8" extent="1.3"/>
+
+  <option wind="5 5 0" density="10">
+    <flag constraint="disable"/>
+  </option>
+
+  <worldbody>
+    <geom name="floor" type="plane" size="0 0 .1"/>
+    <light diffuse=".6 .6 .6" specular="0.2 0.2 0.2" pos="0 0 4" dir="0 0 -1"/>
+    <body name="B0_0" pos="0 0 1">
+      <composite type="cloth" count="9 19 1" spacing="0.05" flatinertia="0.01">
+        <joint kind="main" damping="0.001" stiffness=".1"/>
+        <skin texcoord="true" inflate="0.005" subgrid="4"/>
+        <geom type="ellipsoid" size="0.025 0.01 0.025" rgba=".8 .2 .1 1"/>
+        <tendon kind="main" stiffness="100" damping=".001"/>
+        <tendon kind="shear" stiffness="100" damping=".001"/>
+      </composite>
+    </body>
+  </worldbody>
+</mujoco>
+