Update README.rst

Author: fsbraun

README.rst

@@ -2,7 +2,7 @@
  django CMS Frontend
 #####################
 
-|pypi| |docs| |coverage| |python| |django| |djangocms|
+|pypi| |docs| |coverage| |python| |django| |djangocms| |djangocms4|
 
 **django CMS Frontend** is a plugin bundle which builds on from & improves
 the architecture of `djangocms-bootstrap4 <https://github.com/django-cms/djangocms-bootstrap4>`_.
@@ -180,3 +180,6 @@ See readthedocs for the `documentation
 
 .. |djangocms| image:: https://img.shields.io/badge/django%20CMS-3.8%2B-blue.svg
    :target: https://www.django-cms.org/
+
+.. |djangocms4| image:: https://img.shields.io/badge/django%20CMS-4-blue.svg
+   :target: https://www.django-cms.org/