[iOS] Dark and tinted app icons

[wolflu05]

With iOS18 apple has added support for dark and tinted app icons. It would be nice if those icons could also be added to the inventree app.

Links:

• https://developer.apple.com/design/human-interface-guidelines/app-icons
• https://medium.com/@GuillemBruix/design-your-dark-and-tinted-versions-of-your-app-icon-for-ios-18-827444a31851