[minor] Update the README

Author: stephane-caron

README.md

@@ -6,9 +6,9 @@
 ![Status](https://img.shields.io/pypi/status/robot_descriptions)
 [![Contributing](https://img.shields.io/badge/PRs-welcome-green.svg)](https://github.com/stephane-caron/robot_descriptions.py/tree/master/CONTRIBUTING.md)
 
-Import open source robot descriptions as Python modules. The wrapper automatically downloads and cache files at first import. Most [Awesome Robot Descriptions](https://github.com/robot-descriptions/awesome-robot-descriptions) are available.
+Import open source robot descriptions as Python modules.
 
-All descriptions [load successfully](https://github.com/stephane-caron/robot_descriptions.py#loaders) in PyBullet (URDF) and MuJoCo (MJCF).
+Importing a description for the first time automatically downloads and caches files for future imports. Most [Awesome Robot Descriptions](https://github.com/robot-descriptions/awesome-robot-descriptions) are available. All of them [load successfully](https://github.com/stephane-caron/robot_descriptions.py#loaders) in PyBullet (URDF) and MuJoCo (MJCF).
 
 ## Installation