Enables the mice migration event (#21982)

* Enables the mice migration event

🆑 coiax
add: Additional mice sometimes appear in the maintenance tunnels.
Engineers beware!
/🆑

I probably had too much fun writing this.

* Fixes grammar mistake

OOC: Thunder12345: not more than 15 of rodents

code/modules/events/mice_migration.dm

@@ -1,15 +1,28 @@
 /datum/round_event_control/mice_migration
 	name = "Mice Migration"
 	typepath = /datum/round_event/mice_migration
-	weight = 0
+	weight = 10
 
 /datum/round_event/mice_migration
 	announceWhen = 0
+	var/minimum_mice = 5
+	var/maximum_mice = 15
 
 /datum/round_event/mice_migration/announce()
-	priority_announce("Due to space-winter, a number of rodents have \
-		migrated into the maintenance tunnels.", "Migration Alert",
+	var/cause = pick("space-winter", "budget-cuts", "Ragnarok",
+		"space being cold", "\[REDACTED\]", "climate change",
+		"bad luck")
+	var/plural = pick("a number of", "a horde of", "a pack of", "a swarm of",
+		"a whoop of", "not more than [maximum_mice]")
+	var/name = pick("rodents", "mice", "squeaking things",
+		"wire eating mammals", "\[REDACTED\]", "energy draining parasites")
+	var/movement = pick("migrated", "swarmed", "stampeded", "descended")
+	var/location = pick("maintenance tunnels", "maintenance areas",
+		"\[REDACTED\]", "place with all those juicy wires")
+
+	priority_announce("Due to [cause], [plural] [name] have [movement] \
+		into the [location].", "Migration Alert",
 		'sound/effects/mousesqueek.ogg', 100, 1)
 
 /datum/round_event/mice_migration/start()
-	SSsqueak.trigger_migration(rand(5,15))
+	SSsqueak.trigger_migration(rand(minimum_mice, maximum_mice))