[css-values-4] Update status; add @scottkellum to acks

Author: fantasai

css-values-5/Overview.bs

@@ -15,6 +15,7 @@ Ignored Terms: <spacing-limit>, containing block, property, <wq-name>
 Ignored Vars: Cn+1, n
 Inline Github Issues: no
 Default Highlight: css
+Status Text: <strong>This spec is in the early exploration phase. Feedback is welcome, and and major breaking changes are expected.</strong>
 </pre>
 <pre class='link-defaults'>
 spec:css-color-4; type:property; text:color
@@ -3253,9 +3254,9 @@ Acknowledgments</h2>
 	Guillaume Lebas,
 	L. David Baron,
 	Mike Bremford,
-	and Sebastian Zartner
-	for their comments and suggestions,
-	which have improved Level 5.
+	Sebastian Zartner,
+	and especially Scott Kellum
+	for their ideas, comments, and suggestions for Level 5;
 
 <h2 class="no-num" id="changes">
 Changes</h2>