[css-cascade-5] Clarify that only @layer statement rules are allowed before @import, not empty @layer blocks. w3c#7566

Author: fantasai

css-cascade-5/Overview.bs

@@ -129,7 +129,7 @@ Importing Style Sheets: the ''@import'' rule</h2>
 		as if they were written literally into the stylesheet at the point of the ''@import''.
 
 	Any ''@import'' rules must precede all other valid at-rules and style rules in a style sheet
-	(ignoring ''@charset'' and empty ''@layer'' definitions)
+	(ignoring ''@charset'' and <a href="#layer-empty"><css>@layer</css> statement</a> rules)
 	and must not have any other valid at-rules or style rules between it and previous ''@import'' rules,
 	or else the ''@import'' rule is invalid.
 	The syntax of ''@import'' is:
@@ -1993,11 +1993,12 @@ Changes</h2>
 <h3 id="changes-2022-01">
 Changes since the 13 Jan 2022 Candidate Recommendation Snapshot</h3>
 
-Non-trivial changes since the <a href="CSS Cascading and Inheritance Level 5">Candidate Recommendation Snapshot</a>:
+Non-trivial changes since the <a href="CSS Cascading and Inheritance Level 5">13 January 2022 Candidate Recommendation Snapshot</a>:
 
-<!-- to 11 Jan 2022 -->
+<!-- to 13 Jan 2022 -->
 	* Clarify that all “aliases” of a property are reverted by ''revert''/''revert-layer''.
 	* Clarify that style sheets are ordered in [[final CSS style sheets]] order.
+	* Clarify that only ''@layer'' statement rules are ignored when checking validity of ''@import'', not empty ''@layer'' block rules.
 
 <h3 id="changes-2021-10">
 Changes since the 15 Oct 2021 Working Draft</h3>