minor: Add PyPI downloads badge to the readme

Author: stephane-caron

README.md

@@ -2,8 +2,9 @@
 
 [![Build](https://img.shields.io/github/actions/workflow/status/robot-descriptions/robot_descriptions.py/test.yml?branch=main)](https://github.com/robot-descriptions/robot_descriptions.py/actions)
 [![Coverage](https://coveralls.io/repos/github/robot-descriptions/robot_descriptions.py/badge.svg?branch=main)](https://coveralls.io/github/robot-descriptions/robot_descriptions.py?branch=main)
-[![Conda Version](https://img.shields.io/conda/vn/conda-forge/robot_descriptions.svg)](https://anaconda.org/conda-forge/robot_descriptions)
-[![PyPI version](https://img.shields.io/pypi/v/robot_descriptions)](https://pypi.org/project/robot_descriptions/)
+[![Conda Version](https://img.shields.io/conda/vn/conda-forge/robot_descriptions.svg?color=blue)](https://anaconda.org/conda-forge/robot_descriptions)
+[![PyPI version](https://img.shields.io/pypi/v/robot_descriptions?color=blue)](https://pypi.org/project/robot_descriptions/)
+[![PyPI downloads](https://img.shields.io/pypi/dm/robot_descriptions?color=blue)](https://pypistats.org/packages/robot_descriptions)
 [![Contributing](https://img.shields.io/badge/PRs-welcome-green.svg)](https://github.com/robot-descriptions/robot_descriptions.py/tree/main/CONTRIBUTING.md)
 
 Import open source robot descriptions as Python modules.