Make the swoosh look better on longer words

This change places it in the middle of the word, rather than at the start. A better change would be to have it fill the length of the word, but this is a quick improvement.

Refs #1817

assets/style.css

@@ -2382,6 +2382,7 @@ skip-link {
       block-size: var(--space-xs);
       background-image: url('underline.svg');
       background-repeat: no-repeat;
+      background-size: 100% 100%;
       inset-block-start: 82%;
       inset-inline: 0;
     }