Explicitly mention template images for iconColor

[1ec5]

The “Dynamically style interactive points” example sets the iconColor and iconHaloColor properties on an symbol style layer:

https://github.com/mapbox/ios-sdk-examples/blob/2e26ba925be4c59166b8b47c824aa551da9e5715/Examples/Swift/Markers%20and%20callouts/WebAPIDataExample.swift#L61-L69

But it doesn’t mention that these properties only work if the image is a template image:

https://github.com/mapbox/ios-sdk-examples/blob/2e26ba925be4c59166b8b47c824aa551da9e5715/Examples/Swift/Markers%20and%20callouts/WebAPIDataExample.swift#L36-L38

We should mention this requirement in the comment. Even better, the liner notes could contain a screenshot of the template image setting in Xcode’s asset catalog editor, so that inexperienced iOS developers can more easily find the setting.

/cc @captainbarbosa @friedbunny

[captainbarbosa]

Yes, we should still do this.