[css-color-5] Add row and column headers for MacBeth checker, w3c#7691

Author: Chris Lilley

css-color-5/Overview.bs

@@ -41,6 +41,7 @@ spec:css-color-4; type:value; text:srgb
 	table.deltaE td.dE3 { background: rgb(243, 240, 68)}
 	table.deltaE td.dE4 { background: rgb(243, 202, 68)}
 	table.deltaE td.dE5 { background: rgb(243, 103, 68); color: white}
+	table.deltaE th {text-align: center }
 	/* work-around for https://github.com/tabatkins/bikeshed/issues/1799 */
 	div.example {
 		overflow: visible;
@@ -1799,7 +1800,13 @@ or any other color or monochrome output device which has been characterized.
 
 	<figure id="fig-fogra51-roundtrip">
 		<!-- See file Macbeth.txt in the workings directory for details. -->
-		<img src="images/macbeth-roundtrip.svg" width=670 height=450>
+		<object data="images/macbeth-roundtrip.svg" width="720" height="500">
+			<p>A grid of colored squares. There are six colums,
+				labelled A to F,
+				and four rows,
+				labelled 1 to 4.
+			</p>
+		</object>
 		<figcaption>
 			<p>A color checker, used for ensuring color fidelity
 			in the print and photographic industries.
@@ -1815,6 +1822,16 @@ or any other color or monochrome output device which has been characterized.
 			<p>The table below shows, for each patch, the DeltaE 2000 between the original Lab and the Lab value after round-tripping through CMYK. A DeltaE 2000 of 1 or more is just visible.</p>
 			<table class="deltaE">
 				<tr>
+					<th></th>
+					<th>A</th>
+					<th>B</th>
+					<th>C</th>
+					<th>D</th>
+					<th>E</th>
+					<th>F</th>
+				</tr>
+				<tr>
+					<th>1</th>
 					<td class="dE0">0.06</td>
 					<td class="dE0">0.07</td>
 					<td class="dE0">0.03</td>
@@ -1823,6 +1840,7 @@ or any other color or monochrome output device which has been characterized.
 					<td class="dE0">0.17</td>
 				</tr>
 				<tr>
+					<th>2</th>
 					<td class="dE0">0.03</td>
 					<td class="dE0">0.75</td>
 					<td class="dE0">0.05</td>
@@ -1831,6 +1849,7 @@ or any other color or monochrome output device which has been characterized.
 					<td class="dE0">0.02</td>
 				</tr>
 				<tr>
+					<th>3</th>
 					<td class="dE2">1.9</td>
 					<td class="dE0">0.04</td>
 					<td class="dE0">0.06</td>
@@ -1839,6 +1858,7 @@ or any other color or monochrome output device which has been characterized.
 					<td class="dE0">0.05</td>
 				</tr>
 				<tr>
+					<th>4</th>
 					<td class="dE0">0.03</td>
 					<td class="dE0">0.08</td>
 					<td class="dE0">0.03</td>