Trash contains material (#89667)

## About The Pull Request
Adds small amounts of material to most trash items. Generally, these are
about a 5th of a sheet's worth of either plastic or iron.

NOTE: The trash recycler on the station is 62.5% efficient using default
parts. If you use it you are going to get a sheet after around 8 trash
items, not 5.
## Why It's Good For The Game
Previously the only reward for recycling these items was removing them.
Now you can keep that desk area tidy and help out the station by
providing a small trickle of plastic and iron, just from flushing your
garbage.

The iron isn't a big deal but this is a way for any department to
produce small amounts of plastic, service in particular. It's
labour-intensive and the yields are small, but now clowns can pick up
trash and flush it for materials to make their balloons for example.
Players can even buy food items at the vendors for the sole purpose of
making them into trash and making the trash into plastic, if the
situation is dire.
## Changelog
🆑
balance: Trash items now contain small amounts of material.
/🆑

---------

Co-authored-by: tgstation-ci[bot] <179393467+tgstation-ci[bot]@users.noreply.github.com>

code/game/objects/items/trash.dm

@@ -7,6 +7,7 @@
 	w_class = WEIGHT_CLASS_TINY
 	resistance_flags = FLAMMABLE
 	item_flags = NOBLUDGEON|SKIP_FANTASY_ON_SPAWN
+	custom_materials = list(/datum/material/plastic=SMALL_MATERIAL_AMOUNT*2)
 
 /obj/item/trash/Initialize(mapload)
 	var/turf/T = get_turf(src)
@@ -23,6 +24,7 @@
 /obj/item/trash/raisins
 	name = "\improper 4no raisins"
 	icon_state= "4no_raisins"
+	custom_materials = list(/datum/material/cardboard=SMALL_MATERIAL_AMOUNT*2)
 
 /obj/item/trash/candy
 	name = "candy"
@@ -57,6 +59,7 @@
 /obj/item/trash/popcorn
 	name = "popcorn"
 	icon_state = "popcorn"
+	custom_materials = list(/datum/material/cardboard=SMALL_MATERIAL_AMOUNT*2)
 
 /obj/item/trash/popcorn/caramel
 	name = "empty caramel popcorn"
@@ -75,6 +78,7 @@
 /obj/item/trash/syndi_cakes
 	name = "syndi-cakes"
 	icon_state = "syndi_cakes"
+	custom_materials = list(/datum/material/cardboard=SMALL_MATERIAL_AMOUNT*2)
 
 /obj/item/trash/energybar
 	name = "energybar wrapper"
@@ -84,6 +88,7 @@
 	name = "surplus fleet wrapper"
 	desc = "In the Mothic Fleet every individual wrapper is carefully recycled and repurposed into fresh material. Over here they are more commonly dropped directly onto the floor."
 	icon_state = "moth_ration"
+	custom_materials = list(/datum/material/cardboard=SMALL_MATERIAL_AMOUNT*2)
 
 /obj/item/trash/pistachios
 	name = "pistachios pack"
@@ -96,27 +101,32 @@
 /obj/item/trash/semki/healthy
 	name = "nibbled sunflower seeds"
 	icon_state = "sunseeds"
+	custom_materials = null
 
 /obj/item/trash/tray
 	name = "tray"
 	icon_state = "tray"
 	resistance_flags = NONE
+	custom_materials = list(/datum/material/iron=SMALL_MATERIAL_AMOUNT*4)
 
 /obj/item/trash/candle
 	name = "melted candle"
 	icon = 'icons/obj/candle.dmi'
 	icon_state = "candle4"
+	custom_materials = null
 
 /obj/item/trash/flare
 	name = "burnt flare"
 	icon = 'icons/obj/lighting.dmi'
 	icon_state = "flare-empty"
+	custom_materials = list(/datum/material/iron=SMALL_MATERIAL_AMOUNT*2,/datum/material/glass=SMALL_MATERIAL_AMOUNT,)
 
 /obj/item/trash/can
 	name = "crushed can"
 	icon_state = "cola"
 	resistance_flags = NONE
 	grind_results = list(/datum/reagent/aluminium = 10)
+	custom_materials = list(/datum/material/iron=SMALL_MATERIAL_AMOUNT*2)
 
 /obj/item/trash/can/food
 	icon = 'icons/obj/food/canned.dmi'
@@ -196,6 +206,7 @@
 /obj/item/trash/sticko
 	name = "\improper Sticko box"
 	icon_state = "sticko"
+	custom_materials = list(/datum/material/cardboard=SMALL_MATERIAL_AMOUNT*2)
 
 /obj/item/trash/sticko/matcha
 	icon_state = "sticko_matcha"