[css-color-4] please actually read the explanation of gamut mapping

Author: Chris Lilley

css-color-4/Overview.bs

@@ -4658,6 +4658,8 @@ Gamut Mapping
 <h3 id="gamut-mapping-intro">
 An Introduction to Gamut Mapping</h3>
 
+Note: This section provides important context for the specific requirements described elsewhere in the document.
+
 <p><i>This section is non-normative</i></p>
 
 	When a color in an origin color space