[css-images-4] Explicitly link to CSS Color 4 hue interpolation and handling of missing components, w3c#4928

Author: svgeesus

css-images-4/Overview.bs

@@ -1754,9 +1754,11 @@ Coloring the Gradient Line</h4>
 	the [=gradient line=] is the color of the first <a>color stop</a>,
 	and after the last <a>color stop</a>,
 	the [=gradient line=] is the color of the last <a>color stop</a>.
-	Between two <a>color stops</a>,
+	Between each pair of <a>color stops</a>,
 	the [=gradient line’s=] color is interpolated between the colors of the two <a>color stops</a>,
 	with the interpolation taking place in the specified color space,
+	with missing components handled as defined in [[css-color-4#interpolation-missing]],
+	hue interpolation as defined in [[css-color-4#hue-interpolation]], and
 	using premultiplied alpha, as defined in [[css-color-4#interpolation-alpha]].
 	If no <<color-interpolation-method>> is specified in the gradient function,
 	the color space used for gradient interpolation