added sr-only class to styleguide.css

styleguide-website/styleguide.css

@@ -260,7 +260,7 @@ a {
 }
 
 a:not(.ignore-visited):visited, a.always-visited {
-    color: var(--secondary-highlight-color);
+    color: var(--tertiary-highlight-color);
 }
 
 input {
@@ -391,6 +391,15 @@ hr::after {
     }
 }
 
+#sr-only {
+    position:absolute;
+    left:-10000px;
+    top:auto;
+    width:1px;
+    height:1px;
+    overflow:hidden;
+}
+
 html {
     /* Works around a bug in chromium that makes the site not full width in small preview sizes*/
     position: absolute;