Adds ghost visible countdowns for bombs

🆑 coiax
rscadd: For extra observer drama, ghosts can now visibly see the
countdown of various explosives.
/🆑

- Also updates my build script to take account of the move of dm.sh

code/modules/countdown/countdown.dm

@@ -0,0 +1,55 @@
+/obj/effect/countdown
+	name = "countdown"
+	desc = "We're leaving together\n\
+		But still it's farewell\n\
+		And maybe we'll come back\n\
+		To earth, who can tell?"
+
+	var/last_displayed
+	var/atom/attached_to
+	var/text_color = "#ff0000"
+	invisibility = INVISIBILITY_OBSERVER
+	layer = GHOST_LAYER
+	alpha = 100
+
+/obj/effect/countdown/New(atom/A)
+	. = ..()
+	attach(A)
+
+/obj/effect/countdown/proc/attach(atom/A)
+	attached_to = A
+	loc = get_turf(A)
+	SSfastprocess.processing |= src
+
+/obj/effect/countdown/proc/get_value()
+	// Get the value from our atom
+	return
+
+/obj/effect/countdown/process()
+	if(!attached_to || qdeleted(attached_to))
+		qdel(src)
+	var/new_val = get_value()
+	if(new_val == last_displayed)
+		return
+	last_displayed = new_val
+	if(new_val)
+		var/image/text_image = new(loc = src)
+		text_image.maptext = "<font size=4>[new_val]</font>"
+		text_image.color = text_color
+
+		overlays.Cut()
+		overlays += text_image
+	else
+		overlays.Cut()
+
+/obj/effect/countdown/Destroy()
+	attached_to = null
+	SSfastprocess.processing -= src
+	. = ..()
+
+/obj/effect/countdown/syndicatebomb/get_value()
+	var/obj/machinery/syndicatebomb/S = attached_to
+	if(!istype(S))
+		return
+	else if(S.active)
+		return S.timer