[cssom] Add “unless otherwise specified” since we now specify more th…

…ings. #10901

cssom-1/Overview.bs

@@ -2805,7 +2805,7 @@ follow these rules:
     as a [=list=] of CSS component values |components|
     that, when [=CSS/parsed=] according to the property's grammar,
     would represent that value.
-    Additionally:
+    Additionally, unless otherwise specified:
 
     * If certain component values can appear in any order
         without changing the meaning of the value
@@ -2821,7 +2821,7 @@ follow these rules:
     Note: The rules described here outlines the <em>general principles</em> of serialization.
     For legacy reasons, some properties serialize in a different manner,
     which is intentionally undefined here due to lack of resources.
-    Please consult your local reverse-engineer for details.
+    Please consult that property's specification and/or your local reverse-engineer for details.
 3. Remove any <<whitespace-token>>s from |components|.
 3. Replace each component value in |components|
     with the result of invoking [=serialize a CSS component value=].