[css-scroll-snap] Add a comma.

Author: fantasai

css-scroll-snap/Overview.bs

@@ -295,8 +295,8 @@ Scroll Snapping Rules: the 'scroll-snap-type' property {#snap-type}
 	on its <a>containing block chain</a>
 	is a <a>scroll container</a> with a non-''scroll-snap-type/none'' value for 'scroll-snap-type',
 	that is the box's <dfn export local-lt="snap container">scroll snap container</dfn>.
-	Otherwise, the box has no <a>scroll snap container</a>
-	and its <a>snap positions</a> do not cause snapping.
+	Otherwise, the box has no <a>scroll snap container</a>,
+	and its <a>snap positions</a> do not trigger <a>snapping</a>.
 
 	Advisement:
 	Authors should use mandatory snap positions with consideration of