Document Timer autostart in tool scripts

doc/classes/Timer.xml

@@ -43,6 +43,7 @@
 		<member name="autostart" type="bool" setter="set_autostart" getter="has_autostart" default="false">
 			If [code]true[/code], the timer will start immediately when it enters the scene tree.
 			[b]Note:[/b] After the timer enters the tree, this property is automatically set to [code]false[/code].
+			[b]Note:[/b] This property does nothing when the timer is running in the editor.
 		</member>
 		<member name="one_shot" type="bool" setter="set_one_shot" getter="is_one_shot" default="false">
 			If [code]true[/code], the timer will stop after reaching the end. Otherwise, as by default, the timer will automatically restart.