Followup 6a4b979514
In this commit I changed how we load the selected palette
stylesheet so the system specs would know when the CSS is actually
loaded, however this introduced an issue where the user would see
a FOUC when switching palettes. I also introduced a bug where
if you chose to force dark mode then switched the palette, you would
see light mode instead.
This commit fixes both issues, by swapping the CSS link with a preloaded
one then waiting for the preload before switching the href of the
existing link, and removes `mode` shenanigans causing the light mode
issue.
Martin Brennan
96da1d3439