Fix invslot definitions

datatype/_invslot.lua

@@ -1,7 +1,7 @@
 --- @class invslot
---- @field public ID number ID of this item slot (usable directly by /itemnotify)
+--- @field public ID fun(): integer ID of this item slot (usable directly by /itemnotify)
 --- @field public Item item Item data for the item in this slot
---- @field public Name string For inventory slots not inside packs, the slot name, otherwise NULL
+--- @field public Name fun(): string For inventory slots not inside packs, the slot name, otherwise NULL
 --- @field public Pack invslot Container that must be opened to access the slot with /itemnotify
---- @field public Slot number Slot number inside the pack which holds the item, otherwise NULL
---- @field public ToString number Same as ID
+--- @field public Slot fun(): integer Slot number inside the pack which holds the item, otherwise NULL
+--- @field public ToString fun(): string Same as ID