New Backpack Type: Messenger Bags! (#77871)

## About The Pull Request

![image](https://github.com/tgstation/tgstation/assets/12636964/4a2aa26e-8f5b-4090-b21a-d2c429df1c8d)
From downstream with love! These are mechanically identical to a normal
backpack or satchel, just with more drip.
Also a little bit of :o)

![image](https://github.com/tgstation/tgstation/assets/12636964/6671feda-f11c-4ee3-97b5-ad810b7474f5)
These will exist both in prefs and in drobes/lockers.

![image](https://github.com/tgstation/tgstation/assets/12636964/05478ad1-e7ae-4808-8c97-fdd21fc84474)
Sprites by Zydras.

## Why It's Good For The Game
We love fashion here. We love it so much. And most backpacks are too
in-your-face to fit well with a lot of 'fits.

## Changelog
🆑 Nerev4r & Zydras
image: Adds messenger bags to character setup and drobes/lockers!
/🆑

---------

Co-authored-by: Snakebittenn <12636964+Snakebittenn@users.noreply.github.com>
Co-authored-by: GoldenAlpharex <58045821+GoldenAlpharex@users.noreply.github.com>

code/modules/client/preferences/clothing.dm

@@ -26,9 +26,11 @@
 		GSATCHEL,
 		LSATCHEL,
 		GDUFFELBAG,
+		GMESSENGER,
 		DBACKPACK,
 		DSATCHEL,
 		DDUFFELBAG,
+		DMESSENGER,
 	)
 
 /datum/preference/choiced/backpack/icon_for(value)
@@ -41,6 +43,8 @@
 			return /obj/item/storage/backpack/satchel/leather
 		if (GDUFFELBAG)
 			return /obj/item/storage/backpack/duffelbag
+		if (GMESSENGER)
+			return /obj/item/storage/backpack/messenger
 
 		// In a perfect world, these would be your department's backpack.
 		// However, this doesn't factor in assistants, or no high slot, and would
@@ -52,6 +56,8 @@
 			return /obj/item/storage/backpack/satchel/med
 		if (DDUFFELBAG)
 			return /obj/item/storage/backpack/duffelbag/med
+		if (DMESSENGER)
+			return /obj/item/storage/backpack/messenger/med
 
 /datum/preference/choiced/backpack/apply_to_human(mob/living/carbon/human/target, value)
 	target.backpack = value