custom, reorderable entries

[omichde]

This PR introduces mainly AKSection and AKEntry in order to add custom entires and arbitrary ordering:

• AKSection is the "outer" ordering type
• AKEntry holds individual items within each section
• carefully added a default section list, so client code renders identical
• add as few helper as possible
• slightly tuned macOS appearance to match existing design

Bild.13-14-37.mp4

PS: ideally the existing entries would move into AKSection and AKEntry as well. On top, injecting the whole AKConfiguration should then rather being injected into the environment. All beyond the scope but maybe worth it in the long run.