Visited code links

On Safari (13.1.2, macOS 10.15.6) code in a visited link has a dark border. This doesn’t happen in Firefox (79.0).

The following setting in _config.yml fixes the issue in Safari:

color_scheme: fix-visited

by loading the following CSS:

a:visited code {
  border-color: $border-color;
}

some unlinked code