Add attribute field for items

src/item.s

@@ -1,8 +1,14 @@
+DEF ITEM_ATTRF_NONE EQU 0
+DEF ITEM_ATTRF_USABLE EQU (1 << 0)
+DEF ITEM_ATTRF_WEAPON EQU (1 << 1)
+DEF ITEM_ATTRF_ARMOR EQU (1 << 2)
+
 DEF NEXT_ITEM_ID SET 1
 
 ; Declare a new item
 ; \1 Display name
-; \2 Sprite data filename
+; \2 Attributes
+; \3 Sprite data filename
 MACRO Item
     ASSERT STRLEN("\1") < 16
 
@@ -12,6 +18,8 @@ MACRO Item
     EXPORT {ID_NAME}
     REDEF NEXT_ITEM_ID SET NEXT_ITEM_ID + 1
 
+    DB \2
+
     ; Display name
     DB "\1"
     REPT 16 - STRLEN("\1")
@@ -19,11 +27,11 @@ MACRO Item
     ENDR
 
     ; Sprite data
-    INCBIN \2
+    INCBIN \3
 ENDM
 
 SECTION "Item Data", ROM0
 
 ; NOTE: Macro invocation MUST be indented in order to be expanded correctly
 Items::
-    Item COIN, "png/sprite/item/coin.2bpp"
+    Item COIN, ITEM_ATTRF_NONE, "png/sprite/item/coin.2bpp"