Fix getting stuck at loading (#394)

* Add sandbox settings

* Don't install django 4

Co-authored-by: jmcarcell <jmcarcell@users.noreply.github.com>

django_plotly_dash/templates/django_plotly_dash/plotly_app.html

 <div style="{{dstyle}}">
-  <iframe src="{{app.base_url}}" style="{{istyle}}" frameborder="{{fbs}}" sandbox="allow-downloads"></iframe>
+  <iframe src="{{app.base_url}}" style="{{istyle}}" frameborder="{{fbs}}" sandbox="allow-downloads allow-scripts allow-same-origin"></iframe>
 </div>

requirements.txt

@@ -8,5 +8,5 @@ dpd-components
 dash-bootstrap-components
 
 channels<3.0
-Django>=2.2
+Django>=2.2,<4.0.0
 Flask>=1.0.2