[css-images-4] Add the use of “longer” hue interpolation for the colo…

…r wheel in the example

Fix w3c#1222

css-images-4/Overview.bs

@@ -1701,7 +1701,18 @@ Conic Gradient Examples</h4>
 			width: 200px; height: 200px;
 		</pre>
 
-		<img src="images/conic5.png" alt="" >
+		You can also achieve the same effect using "longer" hue interpolation. This is more concise and makes it easy to switch to other color spaces.
+
+		<pre class=lang-css>
+			background: radial-gradient(closest-side, gray, transparent),
+			            conic-gradient(in hsl longer hue, red 0 100%);
+			transform: scaleX(-1);
+
+			border-radius: 50%;
+			width: 200px; height: 200px;
+		</pre>
+
+		<img src="images/conic5.png" alt="color wheel">
 	</div>
 
 	<div class='example' id='ex-conic-pie'>