[css-scroll-snap] Add some issues.

Author: fantasai

css-scroll-snap/Overview.bs

@@ -529,6 +529,8 @@ Scroll Snapping Alignment: the 'scroll-snap-align' property {#scroll-snap-align}
 	For all of these values,
 	the <a>block</a> or <a>inline</a> axis
 	is relative to the element's parent's <a>writing mode</a>.
+	<span class="issue">Is this the correct writing mode to compute against?
+	Or should it be the scroll container's writing mode?</span>
 
 	The <dfn export>scroll alignment values</dfn> are defined as follows:
 
@@ -723,6 +725,10 @@ Types of Scrolling Gestures {#scroll-types}
 		or another element's <a>snap position</a> might be chosen for that axis,
 		or that axis might not snap at all.
 
+		Issue: Define that the 1D snap position is only valid so long as you can see the element.
+		If it's off-screen, it should probably have no effect--that would be confusing,
+		to snap to a non-visible thing.
+
 	: <dfn export local-lt="2D" lt="2D snap position">2D snap position</dfn>
 	:: A <a>2d snap position</a> indicates a desired <a>snap position</a>
 		in both axises at once,