Give link-buttons an outline in high contrast
Give link-buttons an outline in high contrast

The link-buttons we use in our pill component
have a blue background which shows the area they
occupy by default. In high contrast mode,
backgrounds are hidden so the link-button text
looks like it is floating because you can't see
the edge of their area.

These changes use the trick of adding a
transparent border. This is hidden by default but
displays in high contrast mode to show the edges
of the link-button. I've reduced the padding to
accommodate the extra space it takes up.

alphagov/notifications-admin,alphagov/notifications-admin,alphagov/notifications-admin,alphagov/notifications-admin