Adds onCancelPan optional prop and adds more calls to cancelPan

[alex-bain]

Hello - thank you for building NebulaGL, it is a fantastic library.

This PR contains two small changes:

1. Introduces an optional onCancelPan prop to editable-layer, allowing developers to execute their own logic when NebulaGL determines a map panning operation should be interrupted
2. Adds event.cancelPan() invocations for additional EditModes to ensure event.cancelPan is always being called at the appropriate time

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[ibgreen]

Thanks for opening this. In particular, appreciate that docs were added. Testing interactive functions is tricky, but it possible to add a test case or two?

[ibgreen]

@igorDykhta If possible let's see if we can help @alex-bain land this

@chennney