more tweaaaks

- mice events were nerfed (mostly the amount spawned atm, along with roundstart too)
- added a donator item
- buffed dessert infestation event

code/modules/events/mice_migration.dm

@@ -4,8 +4,8 @@
 	weight = 10
 
 /datum/round_event/mice_migration
-	var/minimum_mice = 5
-	var/maximum_mice = 15
+	var/minimum_mice = 3
+	var/maximum_mice = 8
 
 /datum/round_event/mice_migration/announce(fake)
 	var/cause = pick("space-winter", "budget-cuts", "Ragnarok",