Add instructions for registering Django 404 exception page

[josephmancuso]

Probably as simple as just hooking into another exception handler

[girardinsamuel]

It's a bit more complex actually: https://github.com/django/django/blob/main/django/core/handlers/exception.py#L65

There is a specific handler that is not configurable when in debug mode. The only might be to patch this.

And that makes me think, we need to check that when debug=False, if exceptionite page is still showing up or not !! ⚠️