On macOS, a special permission is needed to access the mail directory.
This commit adds support to help users to add this permission with
a screenshot and guides.
This was a bit involved because the image should only be loaded on macOS
and because loading images in egui is quite a pain.
- Split UI up into multiple states
- Changes throughout the codebase to accomodate that
- All still messy but opening a folder and creating a database works now.
- Split up the app into different app_state states
- Added the `startup` state and the `visualize` state
- lots of changes to support the startup screen / state
- The startup screen is still a hot mess
- changed the config handling