Swtich dark mode automatically according to browser settings.

[Leilei332]

Although dark mode is supported in #40 , it doesn't follow the browser dark mode settings and has to change manually.

[coryalewis]

I'd like to plus one this. And even with the manual toggle that exists, it has to be re-enabled every time I log in.

[simonbaird]

Added the "auto" mode in b926d5c . So now there is "light", "dark", and "auto".

There's an unintended side-effect though from that change - if you have dark mode chosen you get a flash of light mode before it changes. I'll see if I can fix that soon, and also make the preference saved with the user's account so it works across different browsers.

[Leilei332]

Looks like the dark mode won't switch after the page is loaded. It only switch at startup. I think we should use prefer-color-scheme media query instead.

https://developer.mozilla.org/en-US/docs/Web/CSS/@media/prefers-color-scheme

[simonbaird]

I've pushed a few updates just now:

• The "flash of wrong mode" problem should be fixed now
• Tiddlyhost will now remember your preference if you change the mode while logged in. This does mean its possible to see it flip from one to the other when you login. (I think that's okay, but I'm open to suggestions.)
• It doesn't dynamically update if you change the the "prefer-color-scheme" option in your browser, but, if your theme mode is "auto", it will update the next time you load a page. I think that's good enough. I think it's technically possible to have it fully dynamic, but because of the way Bootstrap handles light and dark themeing it's difficult.

Lmk if you notice any problems of unexpected behavior.