Allow the janitor belt to hold one trash bag (#3184)

## About The Pull Request

Allow the janibelt to hold a maximum of one trash bag.

## Why It's Good For The Game


![image](https://github.com/user-attachments/assets/ecadd19f-4283-4bff-8e5a-0142241dc169)

Mike wanted this and it seems like good QOL and if you don't support
this you're basically saying you hate Mike so it's up to you.

## Proof Of Testing

<details>
<summary>Screenshots/Videos</summary>


![image](https://github.com/user-attachments/assets/4fbdf564-cfdf-439d-8f96-8dfefa119504)

</details>

## Changelog

🆑
add: the janitor's belt can now hold a trash bag. just one
/🆑

Co-authored-by: LT3 <83487515+lessthnthree@users.noreply.github.com>

code/game/objects/items/storage/belt.dm

@@ -700,6 +700,14 @@
 	. = ..()
 	atom_storage.max_slots = 6
 	atom_storage.max_specific_storage = WEIGHT_CLASS_NORMAL // Set to this so the  light replacer can fit.
+	// BUBBER EDIT BEGIN - Trash bag on da belt
+	var/static/list/exception_cache = typecacheof(list(
+		/obj/item/storage/bag/trash,
+	))
+	atom_storage.exception_hold = exception_cache
+	atom_storage.exception_max = 1
+	atom_storage.allow_big_nesting = TRUE
+	// BUBBER EDIT END - Trash bag on da belt
 	atom_storage.set_holdable(list(
 		/obj/item/access_key,
 		/obj/item/assembly/mousetrap,