Include custom instance icons in .mrpack exports

[mioxyky]

Please confirm the following.

• I checked the existing issues for duplicate feature requests

What parts of Modrinth is your feature request related too?

No response

Is your suggested feature related to a problem? Please describe.

Currently, when exporting an instance as a .mrpack, the custom instance icon is not included.

Describe the solution you'd like

It would be great if the icon could be exported as well (or through an optional "Include custom icon" checkbox), so importing the pack on another computer preserves the instance's appearance.

This would make .mrpack exports feel more complete and improve sharing, backups, and moving instances between devices.

Describe alternatives you've considered

No response

Additional context

No response