Merge pull request #773 from damien-devpy/missing_import_readme

[readme] Fix missing re_path import

Author: JoelLefkowitz

README.rst

@@ -132,6 +132,7 @@ In ``urls.py``:
 .. code:: python
 
    ...
+   from django.urls import re_path
    from rest_framework import permissions
    from drf_yasg.views import get_schema_view
    from drf_yasg import openapi