Not readable in dark mode

[pchampin]

Bikeshed now generates a responsive page that adapts to the color-theme of the user (light/dark). Which is good.
The problem is that this specification contains a number of inline CSS rules that are not responsive.
E.g., l53-55 of index.bs:

  a[data-link-type=dfn] {
    color: #000000;
  }

In the dark theme, where the background color is also black, those links are invisible :-/

NB: in Firefox dev tools, you can manually switch the color scheme for testing purposes. I expect Chrome and others have a similar functionality.