feat(Halloween): add Dracula dark theme

[jarekdanielak]

Which issue does this PR address?

Add Dracula-inspired dark theme. 🎃

[nikku]

With the theme, did you take inspiration from GitHub or another place? I'm not an expert on "dark modes" and wonder how we go about contrasts. As shown below, GitHub seems to offer slightly better ones:

At the same time, they don't use white, but #f0f6fc as a text color, to be slightly easier to read for the eye.

[jarekdanielak]

I initially looked at the GitHub projects board, but found it a bit too dark, so I crossbred it with Dracula, which is universally loved across the internet.

For the contrast, I just go with the flow, doing no scientific measurements whatsoever.

I tried to use the slightly off-white color, but might've not changed it everywhere.

I'll give it another go... 👻

[jarekdanielak]

In the new update, I tried to rely on the built-in colors, adding an even $darker one. 🖤

I updated the screenshot at the top. WDYT?

[nikku]

Thanks for following up! I think GitHub dark users will feel right at home with the new theme:

I pushed a small amount of additional fixes, and in the future we could consider to be fancy regarding the icon (and favicon), invert them, GitHub style, because this seems like what people are doing. For now, it is working good enough. ⭐

[nikku]

Last fix: Powered by is now slightly better visible in dark mode:

[nikku]

One potential follow-up: Style notifications, which will otherwise still look ugly-White 😉

[nikku]

Released as v0.68.0.