Improve launch screen

[stackotter]

Currently the launch screen is pretty dismal and uninformative. For an example of a SwiftUI progress bar for both downloads and extracting zip see the code for the in-app updater.

• [x] Add progress bars for downloading and extracting the client jar on first launch
• [x] Make loading messages more detailed and informative for both the first launch and subsequent launches

[stackotter]

Maybe even throw in some easter egg loading steps that pop up every so often, such as frying you an egg or something. Especially on first launch to entertain peoples' short attention spans.

[AlbertoSamele]

Will do