[scroll-animations-1] Link to issue for removing timeRange

Author: majido

scroll-animations-1/Overview.bs

@@ -423,6 +423,10 @@ determined not by wall-clock time, but by the progress of scrolling in a
     the mapping is then defined by mapping the scroll distance from
     {{start}} to {{end}}, to the [=effective time range=].
 
+Issue(4862): We are working to remove the need for {{timeRange}} to be declared.
+The most recent work on this involved introduction of the concept of 
+"progress-based animations" to web animations.
+
 </div>
 
 ### Scroll Timeline Offset ### {#scroll-timeline-offset-section}