Fix README.md

Fix readthedocs link and add pypi badge and link

README.md

 mbtrack2
 ========
 
-![GitLab Release](https://img.shields.io/gitlab/v/release/184?gitlab_url=https%3A%2F%2Fgitlab.synchrotron-soleil.fr%2F)
-![PyPI - License](https://img.shields.io/pypi/l/mbtrack2)
-![Read the Docs](https://img.shields.io/readthedocs/mbtrack2)
+[![GitLab Release](https://img.shields.io/gitlab/v/release/184?gitlab_url=https%3A%2F%2Fgitlab.synchrotron-soleil.fr%2F)](https://gitlab.synchrotron-soleil.fr/PA/collective-effects/mbtrack2/-/releases) [![PyPI - Version](https://img.shields.io/pypi/v/mbtrack2)](https://pypi.org/project/mbtrack2/)
+[![PyPI - License](https://img.shields.io/pypi/l/mbtrack2)](https://gitlab.synchrotron-soleil.fr/PA/collective-effects/mbtrack2/-/blob/stable/LICENSE)
+[![Read the Docs](https://img.shields.io/readthedocs/mbtrack2)](https://mbtrack2.readthedocs.io/)
 
 mbtrack2 is a coherent object-oriented framework written in python to work on collective effects in synchrotrons.