Add extra context

[Fethienv]

Add the ability to push extra context:
example

def add_extra_context(self, request):
    
    query = request.GET.copy()

    if not query.get('pop'):
        from django.contrib.admin.sites import site
        return {
            'is_popup': query.get('pop'),
            'is_nav_sidebar_enabled': not query.get('pop'),
            'app_full_list': site.get_app_list(request),
        }
    else:
        return {}
  
FileBrowserSite.add_extra_context = add_extra_context

# My Custom FileBrowser site
custom_site = FileBrowserSite(name='custom_filebrowser', storage=DefaultStorage())