implemented Button2 press on tags for toggletag on the focused client

dwm.1

@@ -47,6 +47,12 @@ and
 .B floating
 mode.
 .TP
+.B Button2
+click on a tag label adds/removes that
+.B tag
+to/from the focused
+.B window.
+.TP
 .B Button3
 click on a tag label adds/removes all windows with that
 .B tag

event.c

@@ -109,10 +109,17 @@ buttonpress(XEvent *e)
 		for(a.i = 0; a.i < ntags; a.i++) {
 			x += textw(tags[a.i]);
 			if(ev->x < x) {
-				if(ev->button == Button1)
+				switch(ev->button) {
+				case Button1:
 					view(&a);
-				else if(ev->button == Button3)
+					break;
+				case Button2:
+					toggletag(&a);
+					break;
+				case Button3:
 					toggleview(&a);
+					break;
+				}
 				return;
 			}
 		}