Draw: Export of circle geometries

[jokd]

Describe the bug
When exporting a circle geometry the resulting feature has no geometry.

To Reproduce
Steps to reproduce the behavior:

1. Draw a circle
2. Export to file

Expected behavior
A circle round and clear.

Additional context
Circles are not standard so the solution is probably to either store the feature as a point with a radius as a property or convert the circle to a polygon on export. One downside of the latter is you won't be able to edit the circle since it is made up of multiple short segments.