[css-images-3] Add an issue to make imaget-set() track srcset/picture.

--HG--
extra : rebase_source : 48f090374b38199f5e0ec2b8765e8406813ccc34

Author: tabatkins

css-images-3/Overview.bs

@@ -280,6 +280,9 @@ Resolution Negotiation: the ''image-set()'' notation {#image-set-notation}
 	<dfn>&lt;image-set-option></dfn> = [ <<image>> | <<string>> ] <<resolution>>
 	</pre>
 
+	Issue: We should add "w" and "h" dimensions as a possibility, and a "format()" function,
+	to match the functionality of HTML's <a element>picture</a>.
+
 	The ''image-set()'' function can not be nested inside of itself,
 	either directly
 	or indirectly