Document the H exemption.

docs/user_editor.html

@@ -242,6 +242,10 @@ The available commands are listed below with explanations.
 <b>        G - Multiple Nodes $
 </b>                Allows user to be logged on to more than one node at a time.
                 This exemption is useful for Guest accounts.
+<b>        H - No inactivity
+</b>                Allows user to be logged for extended inactive periods
+                    without being automatically disconnected.
+<b>        I - Interrupt Nodes $
 <b>        I - Interrupt Nodes $
 </b>		Allows user to interrupt (hang up on) other nodes with the
                 ;INTR command.