Icon auto generation for platforms

[enfipy]

Objective

It would be awesome to make crossbundle generate all necessary icons from one specified icon during a build.

What problem does this solve, or what need does it fill?

Developer Experience with crossbow will be higher - as everything you need - is just one icon.

What solution would you like?

1. The solution should not restrict developers from using custom resource icons. It should be possible to turn off icon generation in Cargo.toml.
2. it should be possible to specify custom icons for iOS and Android.

Icon design specifications:

• https://developer.android.com/distribute/google-play/resources/icon-design-specifications
• https://developer.android.com/guide/practices/ui_guidelines/icon_design_adaptive
• https://developer.apple.com/design/human-interface-guidelines/foundations/app-icons/