Update docs

documentation/lua_api.txt

@@ -701,6 +701,9 @@ Device
 		Sends the given lua *table* to clients connected to the engine.
 		Note that the current version only supports explicitly escaped strings as key/value pairs.
 
+	**can_get** (type, name) : bool
+		Returns whether the resource (type, name) is loaded.
+
 DebugLine
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