Document that preloaded resources are never freed

Author: leandro-benedet-garcia

modules/gdscript/doc_classes/@GDScript.xml

@@ -193,6 +193,7 @@
 			<description>
 				Returns a [Resource] from the filesystem located at [param path]. During run-time, the resource is loaded when the script is being parsed. This function effectively acts as a reference to that resource. Note that this function requires [param path] to be a constant [String]. If you want to load a resource from a dynamic/variable path, use [method load].
 				[b]Note:[/b] Resource paths can be obtained by right-clicking on a resource in the Assets Panel and choosing "Copy Path", or by dragging the file from the FileSystem dock into the current script.
+				[b]Warning:[/b] Preloaded resources will never be freed. This behavior may change in the near future and should not be taken into consideration for your software.
 				[codeblock]
 				# Create instance of a scene.
 				var diamond = preload("res://diamond.tscn").instantiate()