Add debug boot mode

[Arlodotexe]

Background

Right now, when the app is starting up, we display "Quips". These are witty remarks that change depending on language, time of day or year, region, etc., and are meant to entertain the user briefly while the app loads.

Problem

The startup process in the app is a rather complicated one. It would be useful, or at least more entertaining to our advanced users, to have a debug mode which displays log messages while starting up.

Solution

• [ ] Add a "debug" mode to the advanced app settings
• [ ] In AppLoadingView.xaml, display output from the logger either alongside or instead of quips.

Designs can be proposed and discussed below or in the PR, if needed 👇

[Arlodotexe]

The asynchronous splash screen will be removed in 0.1.0, and a live debug feed is made available by the new settings UI.