underline the links in text blocks and lists

[Travel_girl]

At the new rosetta page (​https://test.wordpress.org/) the links are not underlined. If links placed between text, its better to underline them, so user can better recognize links as links. In this case it would be good if we underline the links who are placed in p and li for site-main.

I would recomment to use the usual blue (like the link color) for the underline, instead of the light grey. Cause the color contrast of #bbb does not match AA with the background (​https://contrastchecker.com/).

[SergeyBiryukov]

It's the same on ​https://wordpress.org/, not specific to the new Rosetta theme.

[obenland]

In 6058:

Main: Style updates.

• Fixes a bug where pages were misaligned.
• Underlines links in entry content and lists. Fixes #3216.
• Improves comment metadata and reply.
• Adds wporg header styles in case we ever get to a point where we can ditch wp4.css.

See #2861.