[zIndex] Add support for setting zIndex on markers

[mlanter]

Add support for setting the z-index on markers via the style.

Example usage:

<MapView.Marker
  style={styles.importantMarker}
  ... 
/>

const styles = StyleSheet.create({
  importantMarker: {
    zIndex: 1,
  },
});

Test plan:

• Verify on both iOS and Android that with this fix any markers with a zIndex > 0 show up above any other markers.
• Verify without the change sometimes markers appear below others.

[spikebrehm]

Awesome, thanks! Can you please add an example to the example app demonstrating this feature? We basically use the example app as manual integration tests.

[carleryd]

Great job, just tested it and it works great! I have been wanting this feature for a long time, looking forward to seeing it in the next release!

[mlanter]

Here's an example-

[spikebrehm]

Can you also add this to Google Maps for iOS?

https://github.com/opendoor-labs/react-native-maps/blob/ff85d1f591683703be700c6bd942b665d9c8dc57/ios/AirGoogleMaps/AIRGoogleMapMarkerManager.m

[mlanter]

Yep! Here's iOS screenshots for Apple and Google Maps-

[spikebrehm]

Awesome, thank you so much! 🍻

[spikebrehm]

👍