new documentation and some fixes in code

docs/lua/ItemPrefab.lua

@@ -0,0 +1,28 @@
+-- luacheck: ignore 111
+
+--[[--
+Barotrauma ItemPrefab class with some additional functions and fields
+
+Barotrauma source code: [ItemPrefab.cs](https://github.com/evilfactory/Barotrauma-lua-attempt/blob/master/Barotrauma/BarotraumaShared/SharedSource/Items/ItemPrefab.cs)
+]]
+-- @code ItemPrefab
+
+--- Add ItemPrefab to spawn queue and spawns it at the specified position
+-- @tparam ItemPrefab itemPrefab
+-- @tparam Vector2 position
+-- @tparam function spawned
+-- @realm server 
+function AddToSpawnQueue(itemPrefab, position, spawned) end
+
+--- Add ItemPrefab to spawn queue and spawns it inside the specified inventory
+-- @tparam ItemPrefab itemPrefab
+-- @tparam Inventory inventory
+-- @tparam function spawned
+-- @realm server 
+function AddToSpawnQueue(itemPrefab, inventory, spawned) end
+
+--- Get a item prefab via name or id
+-- @tparam string itemNameOrId
+-- @treturn ItemPrefab
+-- @realm shared 
+function GetItemPrefab(itemNameOrId) end