commented recent Control-shortcut additions

dmenu.1

@@ -66,7 +66,7 @@ Select the first item of the previous/next 'page' of items.
 .B Home/End
 Select the first/last item.
 .TP
-.B Tab
+.B Tab (Control-i)
 Copy the selected item to the input field.
 .TP
 .B Return
@@ -74,13 +74,13 @@ Confirm selection and quit (print the selected item to standard output). Returns
 .B 0
 on termination.
 .TP
-.B Shift-Return
+.B Shift-Return (Control-j)
 Confirm selection and quit (print the text in the input field to standard output).
 Returns
 .B 0
 on termination.
 .TP
-.B Escape
+.B Escape (Control-bracketleft)
 Quit without selecting an item. Returns
 .B 1
 on termination.