[devhelp] Settings: add a TODO comment

[Sébastien Wilmet <swilmet src gnome org>]

commit e629af3b5060cf7835d3d372341595a4b722501b
Author: Sébastien Wilmet <swilmet gnome org>
Date:   Wed Apr 4 14:19:03 2018 +0200

    Settings: add a TODO comment
    
    I will need to figure out how to implement it with DhBookSelection.

 devhelp/dh-settings.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
---
diff --git a/devhelp/dh-settings.c b/devhelp/dh-settings.c
index efe9edd..bd672a2 100644
--- a/devhelp/dh-settings.c
+++ b/devhelp/dh-settings.c
@@ -57,6 +57,9 @@ struct _DhSettingsPrivate {
         GSettings *gsettings_contents;
 
         /* List of book IDs (gchar*) currently disabled. */
+        /* TODO listen to the "books-disabled" GSettings key changes, and add a
+         * ::books-disabled-changed signal or something like that.
+         */
         GList *books_disabled;
 
         guint group_books_by_language : 1;