Added localhost to ALLOWED_HOSTS in settings.py

in order to make it work with GitHub Codespace. It also doesn't break
anything for local environment.

Author: kewtree1408

en/django_start_project/README.md

@@ -111,7 +111,7 @@ match our hostname on PythonAnywhere once we deploy our application so we will c
 
 {% filename %}mysite/settings.py{% endfilename %}
 ```python
-ALLOWED_HOSTS = ['127.0.0.1', '.pythonanywhere.com']
+ALLOWED_HOSTS = ['localhost', '127.0.0.1', '.pythonanywhere.com']
 ```
 
 > **Note**: If you're using a Chromebook, add this line at the bottom of your settings.py file: