Add support for customizable action colors

[micahmo]

Pull Request Description

The PR adds the ability to customize the colors for the following actions in Thuder.

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These colors apply to swipe gestures, inkwells, status indicators, etc. Note that we can pretty easily add more colors in the future. It should also be possible for us to use a similar mechanism to customize other colors in the app (e.g., nested comment indicators or media badge indicators).

Finally, there is a new settings hint in the gestures page which points to this new setting.

As this was quite a big change, please be on the lookout for unusual colors!

Issue Being Fixed

Issue Number: #1301 and #25

Screenshots / Recordings

https://github.com/thunder-app/thunder/assets/7417301/59093405-8eec-4647-a481-7c72e18d5010

Checklist

• [ ] Did you update CHANGELOG.md?
• [ ] Did you use localized strings where applicable?
• [ ] Did you add semanticLabels where applicable for accessibility?

[micahmo]

Could you also add in red as a colour option? This request comes from https://lemmy.world/comment/9492460

Done!

https://github.com/thunder-app/thunder/assets/7417301/d83c5ff1-c304-47a2-a27c-863f19510a3e