[css-color-4] Add oklab() and oklch() in <color> grammar

Author: LeaVerou

css-color-4/Overview.bs

@@ -462,15 +462,17 @@ Representing Colors: the <<color>> type</h2>
 	<dfn>&lt;absolute-color-base></dfn> = <<hex-color>> | <<named-color>> | transparent |
 	    <<rgb()>> | <<rgba()>> | <<hsl()>> | <<hsla()>> | <<hwb()>> |
 	    <<lab()>> | <<lch()>> |
+	    <<oklab()>> | <<oklch()>> |
 	    <<color()>>
 	</pre>
 
 	The <dfn export>color-functions</dfn> are <<rgb()>>, <<rgba()>>,
 		<<hsl()>>, <<hsla()>>, <<hwb()>>,
-		<<lab()>>, <<lch()>>, and
+		<<lab()>>, <<lch()>>,
+		<<oklab()>>, <<oklch()>>, and
 		<<color()>>.
 
-	Of those, <<hsl()>>, <<hsla()>>, <<hwb()>> and <<lch()>>
+	Of those, <<hsl()>>, <<hsla()>>, <<hwb()>>, <<lch()>>, and <<oklch>>
 		are <dfn export>cylindrical polar color</dfn> representations,
 		which specify color using a <<hue>> angle,
 		a central axis representing lightness