[css-view-transitions-2] Align with Web IDL specification (#10123)

Author: autokagami

css-view-transitions-2/Overview.bs

@@ -506,6 +506,7 @@ whose [=ViewTransition/active types=] [=list/contains=] at least one of the <<cu
 The {{ViewTransition}} interface is extended as follows:
 
 <xmp class='idl'>
+[Exposed=Window]
 interface ViewTransitionTypeSet {
 	setlike<DOMString>;
 };