* Enable choosing a high contrast variant of the Light theme
* Updates to high contrast theme to match design and show focus
* Adjust the outline-offset to match designs
* Don't draw an outline around the active tab
* Prevent cropping of outlines on buttons
* Use the correct colour for links
* Change light grey text to be darker in high contrast theme
* Use a darker text colour in admin panel
* Adjust background colours of back button and font slider
