next branch: ThemeSwitch FOUC with SSR

[dimfeld]

ThemeSwitch shows the light mode setting then moves over to dark mode if loading in SSR. This is because the positioning is just using the checked state instead of being keyed on the dark class.

This is a GIF of me refreshing the page three times.

This can probably just be overridden by passing in some custom classes to disable the normal positioning classes and use dark: variant based code instead. I'll make a PR for this soon-ish.

[techniq]

Fixed via #228