[css-color-hdr] Define epsilon for missing hue, w3c#11706

Author: svgeesus

css-color-hdr-1/Overview.bs

@@ -898,6 +898,10 @@ Mixing Dynamic Range Limits: the ''dynamic-range-limit-mix()'' function {#dynami
 				<td>for Jz: 0% = 0.0, 100% = 1.0<br>
 				for Cz: 0% = 0.0, 100% = 0.26</td>
 			</tr>
+			<tr>
+				<th>Powerless hue ε </th>
+				<td>Cz &lt;= 0.0000026</td>
+			</tr>
 		</table>
 
 		<div class="example">