Upgrade dark-light to v2

[Rudxain]

• v2.0.0 rust-dark-light/dark-light#53
• https://github.com/rust-dark-light/dark-light/releases/tag/2.0.0

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• This is only a breaking change due to the version bump, the actual Iced-API is intact.
• I haven't cargo checked, as the repo is too big to git clone (for me). I know I could download without the git log data, but I don't have much time now.
• I formatted the code on the Rust playground

[edwloef]

cargo check, cargo fmt --all -- --check and the tour example run through fine, clippy complains about something but it's unrelated to this pr. This transitively updates zbus to v5 which is definitely nice to have.

[T-256]

Suggested change

	Ok(dark_light::Mode::Light) | Ok(dark_light::Mode::Unspecified) | Err(_) => {
	Theme::Light
	_ => Theme::Light,

[Rudxain]

Personally I would've made this change before even opening the PR, but I decided to preserve the verbosity of the original just-in-case there's a reason for the verbosity

[hecrj]

Thanks!