Introduce “basic” colour theme

[jotaen]

Resolves #325.

This PR introduces a new basic colour theme, which is based on 8-bit ANSI colours. It doesn’t override the default text colour, so the colour of black/white text is “responsive” automatically.

[jotaen]

@vladdeSV if you like, feel free to check out this PR and the new basic colour theme.

[vladdeSV]

I'll give it a go tomorrow! (busy irl rn)

[vladdeSV]

(lol i managed to compile klog on a vps from my phone while in the passenger seat of a car)

Initial impressions are great! Easily readable in both light and dark themes :)

Of course, with mismanaged themes it did become a bit hard to read

[vladdeSV]

Honestly, looks good to me 🙌

I couldn't figure out how to set 8-bit mode, so didn't test that.

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Although unrelated to the PR, is it praxis to use British spelling? Mistyped it as "color_scheme", and this is the first time I've noticed to use British

[jotaen]

Haha, that’s what I call commitment! 😆 (Glad you didn’t drive, though.) Thanks for checking! It also seems to look good on my end.

I couldn't figure out how to set 8-bit mode, so didn't test that.

The basic theme uses an 8-bit colour palette under the hood (for the 8 basic ANSI colours, in contrast to the extended 256 bit colour map). This is only an unimportant implementation detail, though.

Although unrelated to the PR, is it praxis to use British spelling?

I’m personally used to writing British English, and the entire code base uses British spelling.