[scroll-animations-1] Add view-timeline-inset to shorthand

Resolves w3c#8926.

Author: andruud

scroll-animations-1/Overview.bs

@@ -751,16 +751,13 @@ spec:selectors-4; type:dfn; text:selector
 
 	<pre class='propdef shorthand'>
 	Name: view-timeline
-	Value: [ <<'view-timeline-name'>> <<'view-timeline-axis'>>? ]#
+	Value: [ <<'view-timeline-name'>> [ <<'view-timeline-axis'>> || <<'view-timeline-inset'>> ]? ]#
 	Applies to: all elements
 	</pre>
 
 	This property is a [=shorthand=] for setting
-	'view-timeline-name' and 'view-timeline-axis'
+	'view-timeline-name', 'view-timeline-axis', and 'view-timeline-inset'
 	in a single declaration.
-	It does not set 'view-timeline-inset'.
-
-	ISSUE: Should it reset 'view-timeline-inset' also?
 
 # Attaching Animations to [=Scroll-driven Timelines=] # {#scroll-driven-attachment}