[Entity] Add Ian's Backpack (#15519)

* Initial commit

Add Ian's backpack

* Fixed inhand sprites

* Add fill to HoP Locker

Added Ian's 50% probability chance to spawn Ian's backpack in HoP locker

Resources/Prototypes/Entities/Clothing/Back/backpacks.yml

@@ -39,6 +39,18 @@
     storageOpenSound:
       collection: BikeHorn
 
+- type: entity
+  parent: ClothingBackpack
+  id: ClothingBackpackIan
+  name: Ian's backpack
+  description: Sometimes he wears it.
+  components:
+  - type: Sprite
+    sprite: Clothing/Back/Backpacks/ian.rsi
+  - type: Storage
+    storageOpenSound:
+      collection: IanBark
+
 - type: entity
   parent: ClothingBackpack
   id: ClothingBackpackSecurity