[gnome-builder] egg-signal-group: add some overview docs

[Christian Hergert <chergert src gnome org>]

commit 61472ac3f65c5297cb5c9f717363d6880e6faf59
Author: Christian Hergert <christian hergert me>
Date:   Fri May 1 15:55:00 2015 -0700

    egg-signal-group: add some overview docs
    
    Not comprehensive, but better than nothing.

 contrib/egg/egg-signal-group.c |   22 ++++++++++++++++++++++
 1 files changed, 22 insertions(+), 0 deletions(-)
---
diff --git a/contrib/egg/egg-signal-group.c b/contrib/egg/egg-signal-group.c
index a24ebde..f4bb618 100644
--- a/contrib/egg/egg-signal-group.c
+++ b/contrib/egg/egg-signal-group.c
@@ -22,6 +22,28 @@
 
 #include "egg-signal-group.h"
 
+/**
+ * SECTION:egg-signal-group
+ * @title: EggSignalGroup
+ * @short_description: Manage collections of signals on an object
+ *
+ * #EggSignalGroup manages to simplify the process of connecting many signals
+ * to a #GObject as a set.
+ *
+ * In particular, this allows you to:
+ *
+ *  - Block and unblock signals as a group
+ *  - Change the target instance, by disconnecting signals from the old
+ *    instance and connecting to the new instance.
+ *  - Ensuring that blocked signal state transfers across target instances.
+ *
+ * One place you might want to use such a structure is with #GtkTextView and
+ * #GtkTextBuffer. Often times, you'll need to connect to many signals on
+ * #GtkTextBuffer from a #GtkTextView subclass. This allows you to create a
+ * signal group during your instance init function, and simply bind the
+ * #GtkTextView:buffer property to #EggSignalGroup:target.
+ */
+
 struct _EggSignalGroup
 {
   GObject    parent_instance;