ITEM DEFINITIONS
Item definitions are a mapping of "definition IDs" (integers between 1 and 1000000)
to a set of string properties. Some of these properties are required to display items
on the Steam community web site. Other properties can be defined by applications.
Use of these functions is optional; there is no reason to call LoadItemDefinitions
if your game hardcodes the numeric definition IDs (eg, purple face mask = 20, blue
weapon mod = 55) and does not allow for adding new item types without a client patch.
LoadItemDefinitions triggers the automatic load and refresh of item definitions.
Every time new item definitions are available (eg, from the dynamic addition of new
item types while players are still in-game), a SteamInventoryDefinitionUpdate_t
callback will be fired.
