[cssom] Sprinkle some issues.

Author: emilio

cssom-1/Overview.bs

@@ -2789,6 +2789,11 @@ steps:
    <dt><a for="CSSStyleDeclaration">declarations</a>
    <dd>All longhand properties that are <a lt="supported CSS property">supported CSS properties</a>, in lexicographical order, with the value being
    the <a>resolved value</a> computed for <var>obj</var> using the style rules associated with <var>doc</var>.
+
+   Issue: There are UAs that handle shorthands, and all UAs handle shorthands
+   that used to be longhands like 'overflow', see
+   <a href="https://github.com/w3c/csswg-drafts/issues/2529">#2529</a>.
+
    <dt><a for="CSSStyleDeclaration">parent CSS rule</a>
    <dd>Null.
    <dt><a for="CSSStyleDeclaration">owner node</a>
@@ -2800,6 +2805,8 @@ steps:
 <p class=warning>The {{Window/getComputedStyle()}} method exposes information from <a lt="CSS style sheet">CSS style
 sheets</a> with the <a>origin-clean flag</a> unset.
 
+Issue: Should getComputedStyle() provide a useful serialization?
+See <a href="https://github.com/w3c/csswg-drafts/issues/1033">#1033</a>
 
 Utility APIs {#utility-apis}
 ============================