References to `--t-rc-primary` should probably be replaced with `--nz-rc-accent`

[michaellenaghan]

There are 7 references to --t-rc-primary (outside of vars.css). They should probably be replaced with --nz-rc-accent in order to produce correct dark mode behaviour.

[michaellenaghan]

There are also two references to --t-on-primary that should probably be replaced with --nz-rc-base? (Less sure about that one.)

[michaellenaghan]

I also added this rule to tags.css to make the hashmarks visible in dark mode on hover:

.entry-tags a:hover:before {
  color: rgba(var(--nz-rc-base), 0.28);
}