increased key hint size and added borders

[GSI]

IMHO, a link hint size of 9px is eye-strain tiny.

This commit contains some suggested improvements.

[mathstuf]

Not against it, but I'll have to see the change. They were small before so they didn't hide what you were following (a pet peeve of many other implementations of the feature in other browsers). But I can fix my config too :) .

[GSI]

Personally, I realized that I am first looking at which link I want to visit, then I bring up the hints.

Thus, whatever is blocking my view to the original link at that moment is what I want to enter at that point :)

[keis]

Depending on line height used on the page this can cause issues. Or rather cause issues more often simply because more pages will use a font-size smaller than what we use for the hints.

[keis]

A more modest increase to 12x and 1px border should still work pretty well in most cases. WDYT?