[libdazzle] bolding: add comment regarding alignment

[Christian Hergert <chergert src gnome org>]

commit 2b9af1c0321f047177f616da980c5e8ff7685038
Author: Christian Hergert <chergert redhat com>
Date:   Thu May 17 10:23:33 2018 +0100

    bolding: add comment regarding alignment
    
    Fixes #13

 src/widgets/dzl-bolding-label.c | 5 +++++
 1 file changed, 5 insertions(+)
---
diff --git a/src/widgets/dzl-bolding-label.c b/src/widgets/dzl-bolding-label.c
index 374835d..4c2b43e 100644
--- a/src/widgets/dzl-bolding-label.c
+++ b/src/widgets/dzl-bolding-label.c
@@ -31,6 +31,11 @@
  *
  * This might be useful when you want to change a label based on some
  * selection state without it affecting the size request or layout.
+ *
+ * Remember that bold and non-bold variants of fonts can often be very
+ * different in terms of styling. To reduce the chances that you see
+ * shifts in placement, you may want to set the #GtkLabel:xalign or
+ * #GtkLabel:halign properties to 0.0 or %GTK_ALIGN_START respectively.
  */
 
 struct _DzlBoldingLabel