Custom CSS outside container : incalendar.css not updated

Hi there,

I've deployed the container from docker hub (https://registry.hub.docker.com/r/lukdz/oncall/) on latest.

I've modified in db role names and add somes. It seems working very well for the moment.

I'm trying to customize css (outside the container).

I manage to update the oncall.css externally so my left menu is updated.
But I can't manage to modify incalendar.css which is bundeld with oncall.css so none of colors in calendar (with `.inc-event[data-type="Mydatatype"]` selecot) is updated .

I've added in volumes (every thing I found in the container) :

```
/docker/oncall/css/oncall.css:/home/oncall/src/oncall/ui/static/css/oncall.css
/docker/oncall/css/oncall.css:/home/oncall/env/lib/python3.6/site-packages/oncall/ui/static/css/oncall.css
/docker/oncall/css/oncall.css:/home/oncall/source/src/oncall/ui/static/css/oncall.css

/docker/oncall/css/incalendar.css:/home/oncall/src/oncall/ui/static/css/incalendar.css
/docker/oncall/css/incalendar.css:/home/oncall/env/lib/python3.6/site-packages/oncall/ui/static/css/incalendar.css
/docker/oncall/css/incalendar.css:/home/oncall/source/src/oncall/ui/static/css/incalendar.css
```

I do had to reference all oncall.css in order to make it works.

as you can imagine I'm a noob with docker.

Could you point me the right way to do it?

Start by inspecting the Docker image's static CSS locations, especially /home/oncall/src/oncall/ui/static/css/incalendar.css and the corresponding site-packages and source paths listed in the issue. Compare how oncall.css and incalendar.css are loaded and verify the mounted file through the deployed calendar; done means the external incalendar.css changes affect the calendar colors.

Written by the indexing model from the issue text.