feat(ui): Make file types themeable

[cfxegbert]

Addresses issue #235.

[cfxegbert]

Just noticed https://github.com/eza-community/eza/pull/63/files. Should I refactor to be more like #63? Should I rename immediate to build?

[cafkafk]

Should I refactor to be more like #63?

If you wanted to, perhaps you could do so in a follow up PR (which would make it easier to see the diff). I don't think you have too, but maybe I'm missing something.

Should I rename immediate to build?

Build is probably more intuitive, immediate might be more "correct". I may lean slightly to being more intuitive, but I think you should make the pick you prefer tbh.

[PThorpe92]

If you wanted to, perhaps you could do so in a follow up PR (which would make it easier to see the diff).

I have been trying to diff your PR and the old one by switching tabs. and I would heavily agree with this.

I would say that if there is anything you feel 63 does better / cleaner than yours, implement it and they can be essentially merged into one, and we can close 63 in favor of this one 👍

[cafkafk]

LGTM 👍, haven't tested this but have tested that it doesn't seem to break anything.

Sidequest: While you have these parts of the code fresh in your mind, would you like to document them? If not just ping me and I'll merge.

[cafkafk]

Still works for me, and integration tests work, so merging, ty for the PR