Favorite lists (#237)

Remove/show favorites namespace if a task/list is the first to being marked as favorite

Add special case to prevent marking an archived list as favorite

Add marking a task as favorite  on namespaces page

Prevent toggling the favorite state for the favorites list

Add method to toggle list favorite in the menu

Add favorite icon to lists in menu

Co-authored-by: kolaente <k@knt.li>
Reviewed-on: https://kolaente.dev/vikunja/frontend/pulls/237

src/models/list.js

@@ -35,6 +35,7 @@ export default class ListModel extends AbstractModel {
 			hexColor: '',
 			identifier: '',
 			backgroundInformation: null,
+			isFavorite: false,
 
 			created: null,
 			updated: null,