[css-images-3] Separate first and last stop fixing into separate step…

…s, so it's clearer what happens with a single stop. #10092

css-images-3/Overview.bs

@@ -1061,6 +1061,8 @@ Color Stop “Fixup”</h4>
 		<li>
 			If the first <a>color stop</a> does not have a position,
 			set its position to 0%.
+
+		<li>
 			If the last <a>color stop</a> does not have a position,
 			set its position to 100%.