IFeatureFilterEvaluationContext should be exported

[YVbakker]

IFeatureFilter was exported in #27 however when one wants to implement a custom IFeatureFilter, the implementation of evaluateAsyncs context parameter still lacks type information. This type, IFeatureFilterEvaluationContext is not exported from the package.

[zhiyuanliang-ms]

Hey, @YVbakker

Thanks for reaching out. Yes, IFeatureFilterEvaluationContext should be exported as well. That was an oversight. We will fix it!