[css-syntax] Fix #4088: informative serialization table for 4/**/%

Author: SimonSapin

css-syntax-3/Overview.bs

@@ -3295,7 +3295,12 @@ Serialization</h2>
 		</ul>
 
 		<style>
-			#serialization-tables th { font-size: 80%; line-height: normal }
+			#serialization-tables th, #serialization-tables td {
+				font-size: 80%;
+				line-height: normal;
+				padding: 0.5em;
+				text-align: center;
+			}
 		</style>
 
 		<table class='data'>
@@ -3312,39 +3317,40 @@ Serialization</h2>
 				<th>CDC
 				<th>(
 				<th>*
+				<th>%
 			<tr>
 				<th>ident
-				<td>✗<td>✗<td>✗<td>✗<td>✗<td>✗<td>✗<td>✗<td>✗<td>✗<td>
+				<td>✗<td>✗<td>✗<td>✗<td>✗<td>✗<td>✗<td>✗<td>✗<td>✗<td> <td>
 			<tr>
 				<th>at-keyword
-				<td>✗<td>✗<td>✗<td>✗<td>✗<td>✗<td>✗<td>✗<td>✗<td> <td>
+				<td>✗<td>✗<td>✗<td>✗<td>✗<td>✗<td>✗<td>✗<td>✗<td> <td> <td>
 			<tr>
 				<th>hash
-				<td>✗<td>✗<td>✗<td>✗<td>✗<td>✗<td>✗<td>✗<td>✗<td> <td>
+				<td>✗<td>✗<td>✗<td>✗<td>✗<td>✗<td>✗<td>✗<td>✗<td> <td> <td>
 			<tr>
 				<th>dimension
-				<td>✗<td>✗<td>✗<td>✗<td>✗<td>✗<td>✗<td>✗<td>✗<td> <td>
+				<td>✗<td>✗<td>✗<td>✗<td>✗<td>✗<td>✗<td>✗<td>✗<td> <td> <td>
 			<tr>
 				<th>#
-				<td>✗<td>✗<td>✗<td>✗<td>✗<td>✗<td>✗<td>✗<td> <td> <td>
+				<td>✗<td>✗<td>✗<td>✗<td>✗<td>✗<td>✗<td>✗<td> <td> <td> <td>
 			<tr>
 				<th>-
-				<td>✗<td>✗<td>✗<td>✗<td>✗<td>✗<td>✗<td>✗<td> <td> <td>
+				<td>✗<td>✗<td>✗<td>✗<td>✗<td>✗<td>✗<td>✗<td> <td> <td> <td>
 			<tr>
 				<th>number
-				<td>✗<td>✗<td>✗<td>✗<td> <td>✗<td>✗<td>✗<td> <td> <td>
+				<td>✗<td>✗<td>✗<td>✗<td> <td>✗<td>✗<td>✗<td> <td> <td> <td>✗
 			<tr>
 				<th>@
-				<td>✗<td>✗<td>✗<td>✗<td>✗<td> <td> <td> <td> <td> <td>
+				<td>✗<td>✗<td>✗<td>✗<td>✗<td> <td> <td> <td> <td> <td> <td>
 			<tr>
 				<th>.
-				<td> <td> <td> <td> <td> <td>✗<td>✗<td>✗<td> <td> <td>
+				<td> <td> <td> <td> <td> <td>✗<td>✗<td>✗<td> <td> <td> <td>
 			<tr>
 				<th>+
-				<td> <td> <td> <td> <td> <td>✗<td>✗<td>✗<td> <td> <td>
+				<td> <td> <td> <td> <td> <td>✗<td>✗<td>✗<td> <td> <td> <td>
 			<tr>
 				<th>/
-				<td> <td> <td> <td> <td> <td> <td> <td> <td> <td> <td>✗
+				<td> <td> <td> <td> <td> <td> <td> <td> <td> <td> <td>✗<td>
 		</table>
 	</div>