Add CSS for <mark> elements.

Will be using them in a future post.

assets/css/dark.css

@@ -18,6 +18,11 @@
 		color: #e6e6e6;
 	}
 
+	mark {
+		color: #000;
+		background-color: #eee7b2;
+	}
+
 	/* Only color <a> if it's a link; if href is empty, let it be. */
 	a:link {
 		color: #eee7b2;

assets/css/main.css

@@ -324,6 +324,7 @@ pre {
  * This is Technique C25 of SC 1.4.8 */
 input,
 img,
+mark, /* borders provide a distinguishing factor besides color */
 pre,
 summary {
 	border: 1px solid;