Add new differentiable physics tutorial to readme.

PiperOrigin-RevId: 631458983
Change-Id: Ic0ef9e93397a974be50f0616571a4a5fea6f2b21

mjx/training_apg.ipynb

@@ -1,6 +1,39 @@
 {
  "cells": [
   {
+    "cell_type": "markdown",
+    "metadata": {
+     "id": "MpkYHwCqk7W-"
+    },
+    "source": [
+     "![MuJoCo banner](https://raw.githubusercontent.com/google-deepmind/mujoco/main/banner.png)\n",
+     "\n",
+     "# <h1><center>Tutorial  <a href=\"https://colab.research.google.com/github/google-deepmind/mujoco/blob/main/mjx/training_apg.ipynb\"><img src=\"https://colab.research.google.com/assets/colab-badge.svg\" width=\"140\" align=\"center\"/></a></center></h1>\n",
+     "\n",
+     "This notebook provides a tutorial for differentiable physics for policy learning in [**MuJoCo XLA (MJX)**](https://github.com/google-deepmind/mujoco/blob/main/mjx), a JAX-based implementation of MuJoCo.\n",
+     "\n",
+     "**A Colab runtime with GPU acceleration is required.** If you're using a CPU-only runtime, you can switch using the menu \"Runtime > Change runtime type\".\n",
+     "\n",
+     "\n",
+     "This notebook was written by [Jing Yuan Luo](https://github.com/Andrew-Luo1).\n",
+     "\n",
+     "\u003c!-- Copyright 2021 DeepMind Technologies Limited\n",
+     "\n",
+     "     Licensed under the Apache License, Version 2.0 (the \"License\");\n",
+     "     you may not use this file except in compliance with the License.\n",
+     "     You may obtain a copy of the License at\n",
+     "\n",
+     "         http://www.apache.org/licenses/LICENSE-2.0\n",
+     "\n",
+     "     Unless required by applicable law or agreed to in writing, software\n",
+     "     distributed under the License is distributed on an \"AS IS\" BASIS,\n",
+     "     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.\n",
+     "     See the License for the specific language governing permissions and\n",
+     "     limitations under the License.\n",
+     "--\u003e"
+    ]
+   },
+   {
    "cell_type": "markdown",
    "metadata": {},
    "source": [