[Hinode] Add underline to links

[timcappalli]

Currently links just go bold on hover. This fails WCAG accessibility checks. Change to underline.

To ensure links are accessible within text blocks:

• Ensure that links have sufficient contrast between the link text and the surrounding text. Use underlines or bold styles to make links easily distinguishable.
• Avoid relying solely on color to distinguish links from surrounding text.
• Use CSS to underline or otherwise style links differently from the surrounding text.