Add underline to high contrast text when prefers-contrast is active

[jason-me]

Adds an underline to high contrast link text in the guide body when prefers-contrast is active as set by the user in their OS settings.

As per previous discussion: #1015 (comment)

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[jason-me]

@GBKS - You mentioned the need for this in a previous thread.

[GBKS]

Awesome, thanks for tackling this one. Just one question, why the 2px thickness instead of 1px?

[jason-me]

That was just to make it stand out a bit more for someone who is already using enhanced contrast accessibility settings. 1px should work here too.

[jason-me]

Here is how it looks with a 1px offset and thickness instead. Went ahead and changed the values in another commit to this PR. Open to any other sugggestions.

[GBKS]

Thanks, it was actually just a question out of curiosity. I'm happy to go with either option, just let me know which one you think works better.

[jason-me]

Let's go with the the second, more subtle approach since it is not required to make it stand out so much.
https://www.w3.org/WAI/WCAG22/Techniques/general/G182.html

[GBKS]

Thank you for taking care of this. Very much appreciate it.