add embedding support with -w option

dmenu.1

@@ -20,6 +20,8 @@ dmenu \- dynamic menu
 .IR color ]
 .RB [ \-sf
 .IR color ]
+.RB [ \-w
+.IR windowid ]
 .P
 .BR dmenu_run " ..."
 .SH DESCRIPTION
@@ -75,6 +77,9 @@ defines the selected foreground color.
 .TP
 .B \-v
 prints version information to stdout, then exits.
+.TP
+.BI \-w " windowid"
+embed into windowid.
 .SH USAGE
 dmenu is completely controlled by the keyboard.  Items are selected using the
 arrow keys, page up, page down, home, and end.