Comment 1 for bug 2043238

Branch here: https://git.evergreen-ils.org/?p=working/Evergreen.git;a=shortlog;h=refs/heads/user/sleary/lp2043238-color-contrast-tab-links

This just adds .nav-link to our existing color definitions; I'll clean up the variables in bug 2023449.

Testers can inspect links in tabs and check the styles; the color should now be #0A58CA when not focused/hovered and #0848A5 on focus/hover.