docs: update README.rst

Author: jourdain

README.rst

@@ -1,4 +1,6 @@
-trame-vuetify: Material Design widgets for trame
+.. |pypi_download| image:: https://img.shields.io/pypi/dm/trame-vuetify
+
+trame-vuetify: Material Design widgets |pypi_download|
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 .. image:: https://github.com/Kitware/trame-vuetify/actions/workflows/test_and_release.yml/badge.svg