Callout bubble in dark mode should have a dark background

[muffix]

Is your feature request related to a problem? Please Describe.

The bubble background should be dark, but is actually light.

Despite allowing arbitrary views, the callout bubble that drawn by react-native-maps does not seem to allow for a customisation of the border colour. It remains white even in dark mode. We can make the background dark, but it doesn't look right with a white border.

Describe the solution you'd like

Ideally, react-native-maps would allow us to customise the border colour.

Alternatively, we can completely replace the bubble with a custom view by setting the tooltip prop. This allows for completely custom views, including self-drawn bubbles.

Describe alternatives you've considered

Apply the (presumed to be) correct styling to the callout, but the border remains white.
Additional context

It seems that the colour is hard-coded and cannot be overridden in React: https://github.com/react-native-maps/react-native-maps/blob/c447dea5eb4551440b131e3003ac50e0c5709fa9/ios/AirMaps/Callout/SMCalloutView.m#L607