Typo in relevance_indicator parameter (unselectedolor)

Sorry for raising this and not fixing it. If no one gets to it I will sort it when I get a chance. I wouldn't normally raise it by m VS Code spell check is triggering my OCD ;) 

`unselectedolor` should be `unselectedColor`

`macos_ui: ^1.5.1`

https://github.com/GroovinChip/macos_ui/blob/dev/lib/src/indicators/relevance_indicator.dart#L23