Add popup allowing users to choose between two UI modes.

[THEGOLDENPRO]

Display a popup allowing users to choose between two different UI modes, minimalist mode and standard mode, minimalist mode is essentially what we have right now where every UI widget is hidden by default except the image itself. Standard mode will add a "Open Image" or "Select Image" button under the rose in the home screen and will also by default enable some UI elements like the controls floating panel. We should use an egui image button to show a preview of the two different designs.

[THEGOLDENPRO]

It's proving really difficult to layout the modal the way I want it so I'm gonna go ahead and skip this feature for 0.1-alpha.17 (#62).

[THEGOLDENPRO]

Was not meant to close this.

[THEGOLDENPRO]

Found some source code that could help me with performing the layout I want: https://github.com/mq1/TinyWiiBackupManager/blob/main/src/ui/games_grid.rs