[css-color-4] Add id to <color-interpolation-method> token

Author: LeaVerou

css-color-4/Overview.bs

@@ -5006,7 +5006,7 @@ Color space for interpolation</h3>
 		<dfn export>&lt;rectangular-color-space></dfn> = srgb | lab | oklab | xyz | xyz-d50 | xyz-d65
 		<dfn export>&lt;polar-color-space></dfn> = hsl | hwb lch | oklch
 		<dfn export>&lt;hue-interpolation-method></dfn> = [ shorter | longer | increasing | decreasing | specified ] hue
-		<dfn export>&lt;color-interpolation-method> = in [ <<rectangular-color-space>> | <<polar-color-space>> <<hue-interpolation-method>>? ]
+		<dfn export id="color-interpolation-method">&lt;color-interpolation-method> = in [ <<rectangular-color-space>> | <<polar-color-space>> <<hue-interpolation-method>>? ]
 	</pre>
 
 	<p dfn-type=value dfn-for="<color-space>">