docs: --counter option

Author: sand4rt

man/bemenu.1.scd.in

@@ -114,6 +114,9 @@ list of executables under PATH and the selected items are executed.
 :  Only display a scrollbar when the number of items exceeds the number
    of lines.
 
+*--counter* _none_|_always_
+	display a matched/total items counter.
+
 *-e, --vim-esc-exits*
 	Exit bemenu when pressing escape in normal mode for vim bindings.