[css-color-4] add image state

Author: svgeesus

css-color-4/Overview.bs

@@ -3101,6 +3101,7 @@ Predefined colorspaces: ''srgb'', ''display-p3'', ''a98-rgb'', ''prophoto-rgb'',
 				<tr><th>Transfer function</th><td colspan="2">see below</td></tr>
 				<tr><th>White luminance</th><td colspan="2">80.0 cd/m<sup>2</sup></td></tr>
 				<tr><th>Black luminance</th><td colspan="2">0.80 cd/m<sup>2</sup></td></tr>
+				<tr><th>Image state</th><td colspan="2">display-referred</td></tr>
 			</table>
 
 			<pre class="lang-javascript">
@@ -3141,6 +3142,7 @@ Predefined colorspaces: ''srgb'', ''display-p3'', ''a98-rgb'', ''prophoto-rgb'',
 				<tr><th>Transfer function</th><td colspan="2">same as srgb</td></tr>
 				<tr><th>White luminance</th><td colspan="2">80.0 cd/m<sup>2</sup></td></tr>
 				<tr><th>Black luminance</th><td colspan="2">0.80 cd/m<sup>2</sup></td></tr>
+				<tr><th>Image state</th><td colspan="2">display-referred</td></tr>
 			</table>
 
 			<figure>
@@ -3184,6 +3186,7 @@ Predefined colorspaces: ''srgb'', ''display-p3'', ''a98-rgb'', ''prophoto-rgb'',
 				<tr><th>Transfer function</th><td colspan="2">256/563 </td></tr>
 				<tr><th>White luminance</th><td colspan="2">160.0 cd/m<sup>2</sup></td></tr>
 				<tr><th>Black luminance</th><td colspan="2">0.5557 cd/m<sup>2</sup></td></tr>
+				<tr><th>Image state</th><td colspan="2">display-referred</td></tr>
 			</table>
 
 			<figure>
@@ -3235,6 +3238,7 @@ Predefined colorspaces: ''srgb'', ''display-p3'', ''a98-rgb'', ''prophoto-rgb'',
 					<tr><th>Transfer function</th><td colspan="2">see below </td></tr>
 					<tr><th>White luminance</th><td colspan="2">160.0 to 640.0 cd/m<sup>2</sup></td></tr>
 					<tr><th>Black luminance</th><td colspan="2">See text</td></tr>
+					<tr><th>Image state</th><td colspan="2">display-referred</td></tr>
 				</table>
 
 				<pre class="lang-javascript">
@@ -3281,6 +3285,7 @@ Predefined colorspaces: ''srgb'', ''display-p3'', ''a98-rgb'', ''prophoto-rgb'',
 				<tr><th>Blue chromaticity</th><td>0.131</td><td>0.046</td></tr>
 				<tr><th>White chromaticity</th><td>0.3127</td><td>0.3290</td><td>(D65)</td></tr>
 				<tr><th>Transfer function</th><td colspan="2">1/2.4 (see note)</td></tr>
+				<tr><th>Image state</th><td colspan="2">display-referred</td></tr>
 			</table>
 
 			Note: rec2020 references a different transfer curve for cameras. However