Make bits-description table separations more visible

[vizigr0u]

The tables showing the bit layout can be a bit hard to read sometimes because of the low contrast and very thin lines separating each field.
e.g.

(Issue exists for every theme)

Example of what a higher contrast would look like on the navy skin:

(changing --table-border-color to hsl(210, 25%, 33%) from hsl(210, 25%, 13%))

[ISSOtm]

Yeah, seems fair. Can you open a PR?

[vizigr0u]

Yeah, seems fair. Can you open a PR?

I quickly searched the repo for --table-border-color and couldn't find it so I figured it would be much faster for someone with the setup on their machine

[ISSOtm]

Yeah, those are provided by mdBook; those can be overridden (e.g. .ayu .bit-descrs) in custom/style.css.

[vizigr0u]

gotcha, I will try to get the repo setup on my machine and I'll make a PR

[ISSOtm]

Fixed by #531.