based on the feedback:
 - The tool still generates an image by default, rather than a package.
    This will surprise many users, especially those who just want to do
    something simple and straightforward. The least-surprising default
    behavior would be to generate a package of the type most suitable for
    the current platform. An option to generate just an image would be
    fine, for those who want to tweak it before the actual packaging
    step, but that shouldn’t be the default.

  - Related to the previous point, I should only have to specify the
    `--package-type` option if I want something other than the default
    for the current platform.

we are planing to :
1.) add "app-image" as a valid value for --package-type option on all platforms, meaning create an app-image instead of a package. (This used to be the behavior when no --package-type option was given.

2.) Create "default" package-type values on a per-platform basis as follows:
- Debian Linux : "deb"
- Other Linux : "rpm"
- macOS : "dmg"
- Windows : "exe"

When no --package-type option is used, the above defaults will be built.
If "--package-type app-image" is used only an application image will be created.