Video Object Segmentation

**Is your feature request related to a problem? Please describe.**
With video data and applications on the rise, a video object segmentation interface would be really helpful.

**Describe the solution you'd like**
Polygonal annotation for video frames.
Something like VideoPolygon in addition to the currently available VideoRectangle.
VideoRectangle enables VOT (Video Object Tracking)
VideoPolygon will enable the other major task, VOS (Video Object Segmentation).

**Describe alternatives you've considered**
Tried using custom templates with Video Object tag and PolygonLabels control tag, but it doesn't work.
Interface shoes error that PolygonLabels can only control image, not video.

**Additional context**
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