Enhance 'Import a layer from a GeoJSON file' feature?

[elliot-100]

From my experimentation, I think that 'Import a layer from a GeoJSON file' only supports data previously exported with Export Layers to GeoJSON. Is that correct?

It would be interesting to support a wider dialect of GeoJSON, e.g. some of the layers exported by https://github.com/gruppe-adler/grad_meh (sample data: https://github.com/gruppe-adler/meh-data).