[css-anchor-1] Add an issue pointing to w3c#8180

Author: tabatkins

css-anchor-1/Overview.bs

@@ -156,9 +156,17 @@ The ''anchor()'' function has three arguments:
 	If omitted,
 	it defaults to ''0px''.
 
+Issue: Computed value for anchor()
+probably needs to be the anchor() function,
+but with the target anchor element resolved.
+This allows for transitions to work properly
+with tree-scoped names,
+and with changing anchor elements.
+See <a href="https://github.com/w3c/csswg-drafts/issues/8180">Issue 8180</a>.
+
 An ''anchor()'' function representing a [=valid anchor query=]
-resolves to the <<length>>
-that would align the edge
+resolves at [=used value=] time
+to the <<length>> that would align the edge
 of the positioned elements' [=inset-modified containing block=]
 corresponding to the property the function appears in
 with the specified border edge of the [=target anchor element=],