[css-values-4] Make into a note w3c#9301

Author: fantasai

css-values-4/Overview.bs

@@ -1170,7 +1170,8 @@ URL Processing Model</h4>
 	must be omitted
 	(i.e. use the default, UTF-8),
 	regardless of the stylesheet encoding.
-	In other words, a URL written in CSS
+
+	Note:In other words, a URL written in CSS
 	will always [=string/percent-encode after encoding|percent-encode=] non-ASCII codepoints
 	using UTF-8 in the [=URL=] object
 	(and thus whenever using the [=URL=] value for e.g. network requests),