Option to disable appearance change on focus change

[vin047]

Users can disable the appearance change on focus change that currently takes place. Helps the user pay more attention to the timer.

Depends on #125.

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[karbassi]

Thanks for all the PRs. I'm excited to see another dev adding to the project! 🎉

Could you make each PR self-containing without the requirement of another PR. That way we can review the PR on the changes (what it fixes or what new features it implements) without having to merge another PR. I understand there will be repeat code.

[vin047]

Hey @karbassi, thanks for the warm welcome. Glad I can contribute to this project!

Screenshots

Screenshots below for when the app goes out of focus.

Current behaviour

This PR

Its an optional setting, and defaults to the current behaviour, so shouldn't affect other people if they don't like it.

PR dependency

Could you make each PR self-containing without the requirement of another PR. That way we can review the PR on the changes (what it fixes or what new features it implements) without having to merge another PR. I understand there will be repeat code.

The first 2 commits of all the PRs I've submitted are actually all the same (adds the View menu option and saves/loads preferences from UserDefaults) – in other words, the PRs are already self-contained and can be merged without needing #125. I only split it up like that to make it easier for code review. But happy to close that PR if you prefer.

Let me know if this is ok. I'll then fix up the lint issues that have been flagged.