- Added the `image_type` parameter to `DiskMap` which can be set to *'polarized'* or *'total'*.
- Refactored part of `deproject_disk` into the `sort_disk` method to reduce the complexity.
- The output of `phase_function` depends on `image_type`.
- Created a logo for the documentation page.
- Updated the documentation and tutorial.
- Some minor maintenance.