Merge pull request #33945 from Calinou/doc-viewportcontainer-stretch

Document the `ViewportContainer.stretch_shrink` property

doc/classes/ViewportContainer.xml

@@ -15,6 +15,9 @@
 			If [code]true[/code], the viewport will be scaled to the control's size.
 		</member>
 		<member name="stretch_shrink" type="int" setter="set_stretch_shrink" getter="get_stretch_shrink" default="1">
+			Divides the viewport's effective resolution by this value while preserving its scale. This can be used to speed up rendering.
+			For example, a 1280×720 viewport with [member stretch_shrink] set to [code]2[/code] will be rendered at 640×360 while occupying the same size in the container.
+			[b]Note:[/b] [member stretch] must be [code]true[/code] for this property to work.
 		</member>
 	</members>
 	<constants>