[css-conditional-5] Add 'both' value for snapped query #11181 (#11294)

Co-authored-by: Rune Lillesveen <futhark@google.com>

Author: lilles

css-conditional-5/Overview.bs

@@ -1451,7 +1451,7 @@ Scroll snapping: the '@container/snapped' feature</h4>
 	<pre class="descdef mq">
 		Name: snapped
 		For: @container
-		Value: none | x | y | block | inline
+		Value: none | x | y | block | inline | both
 		Type: discrete
 	</pre>
 
@@ -1481,6 +1481,11 @@ Scroll snapping: the '@container/snapped' feature</h4>
 			'@container/snapped' [=container feature=] matches ''inline''
 			if the [=query container=] is a [=snap target=] for its [=scroll container=]
 			in the inline direction of the [=snap container=].
+		<dt><dfn>both</dfn>
+		<dd>
+			'@container/snapped' [=container feature=] matches ''both''
+			if the [=query container=] is a [=snap target=] for its [=scroll container=]
+			in both directions of the [=snap container=].
 	</dl>
 
 <h4 id="scrollable">