Give admins the ability to put a popup notice for players in tickets (#61010)

Admins can now give players a popup if they are not responding to tickets.
Popup is cleared when player replies or ticket is resolved/closed.
As more and more of the chat screen is made irrelevant, new players read it less and less.
This means that a lot of new players are ignoring ahelps, which is something I've encountered myself.

code/modules/admin/verbs/adminhelp.dm

@@ -254,6 +254,9 @@ GLOBAL_DATUM_INIT(ahelp_tickets, /datum/admin_help_tickets, new)
 	if(state == AHELP_ACTIVE)
 		. += ClosureLinks(ref_src)
 
+		if (CONFIG_GET(flag/popup_admin_pm))
+			. += " (<A HREF='?_src_=holder;[HrefToken(TRUE)];adminpopup=[REF(initiator)]'>POPUP</A>)"
+
 //private
 /datum/admin_help/proc/ClosureLinks(ref_src)
 	if(!ref_src)
@@ -345,6 +348,8 @@ GLOBAL_DATUM_INIT(ahelp_tickets, /datum/admin_help_tickets, new)
 	if(initiator && initiator.current_ticket == src)
 		initiator.current_ticket = null
 
+	SEND_SIGNAL(src, COMSIG_ADMIN_HELP_MADE_INACTIVE)
+
 //Mark open ticket as closed/meme
 /datum/admin_help/proc/Close(key_name = key_name_admin(usr), silent = FALSE)
 	if(state != AHELP_ACTIVE)