more simplemobs including slimes fit in pet carriers (#12494)

* make slimes small

* cockroaches/crabs/sloths

code/modules/mob/living/simple_animal/friendly/cockroach.dm

@@ -23,6 +23,7 @@
 	speak_emote = list("chitters")
 	density = FALSE
 	ventcrawler = VENTCRAWLER_ALWAYS
+	mob_size = MOB_SIZE_TINY
 	gold_core_spawnable = FRIENDLY_SPAWN
 	verb_say = "chitters"
 	verb_ask = "chitters inquisitively"

code/modules/mob/living/simple_animal/friendly/crab.dm

@@ -22,6 +22,7 @@
 	friendly_verb_continuous = "pinches"
 	friendly_verb_simple = "pinch"
 	ventcrawler = VENTCRAWLER_ALWAYS
+	mob_size = MOB_SIZE_TINY
 	var/obj/item/inventory_head
 	var/obj/item/inventory_mask
 	gold_core_spawnable = FRIENDLY_SPAWN

code/modules/mob/living/simple_animal/friendly/sloth.dm

@@ -17,6 +17,7 @@
 	response_disarm_simple = "gently push aside"
 	response_harm_continuous = "kicks"
 	response_harm_simple = "kick"
+	mob_size = MOB_SIZE_SMALL
 	mob_biotypes = MOB_ORGANIC|MOB_BEAST
 	gold_core_spawnable = FRIENDLY_SPAWN
 	melee_damage_lower = 18

code/modules/mob/living/simple_animal/slime/slime.dm

@@ -3,6 +3,7 @@
 	icon = 'icons/mob/slimes.dmi'
 	icon_state = "grey baby slime"
 	pass_flags = PASSTABLE
+	mob_size = MOB_SIZE_SMALL
 	ventcrawler = VENTCRAWLER_ALWAYS
 	gender = NEUTER
 	var/is_adult = 0