Lasso Tool for Image Segmentation

**Is your feature request related to a problem? Please describe.**
In image annotation, I see we currently have polygons and brushes for segmentation. But in my scenario, we have curvy irregular objects that is difficult to annotate with polygons (curves need a lot of points to be accurate) or masks (need to change brush size very often). For the sake of annotation accuracy, I'm opting for brushes, but this is making annotation really tedious.

**Describe the solution you'd like**
A lasso tool that allows the annotator to trace the contour of the object would solve this issue.