ol.format.KML feature writers can now export ExtendedData
Keys in the properties object will be exported in the ExtendedData node unless they are part of another export method.
Support for typed data and arbitrary XML data should be added.
add ol.format.XSD CDATA writer
node factories, serializers, and writers for exporing ExtendedData
export ExtendedData tests
use feature geometry in filter
This looks great @raiyni. Thanks for the solid contribution!