Roofs shape in 3D building preview

[Andygol]

Description

Re https://github.com/facebook/Rapid/discussions/993

As of now, there is almost no convenient tool for visualizing the shape of roofs during 3D modeling of buildings before saving the data in the database. It seems that a similar plugin in JOSM is currently in the process of being redesigned, and it does not work as expected. It would be nice to be able to preview buildings with LOD2+ before sending them to an upstream DB and not wait for third party tools like https://osmbuildings.org and https://demo.f4map.com/ to render.

It would be great to have roof shape support in the next release of RapiD.