[css-color] Use a BFC-creating fallback display for the colortables, so the floats don't mess up subsequent sections.

Author: tabatkins

css-color/Overview.bs

@@ -22,7 +22,7 @@ table.named-color-table td:nth-child(-n+2) { border:1px solid black; }
 table.named-color-table td:nth-child(n+4) { background: silver; }
 .color-table {
 	background: #808080;
-	display: block;
+	display: table;
 	display: flex;
 	flex-flow: row wrap;
 	justify-content: space-around;