Create QGIS plugin for get_buildings

[cholmes]

This is technically outside the scope of this project, as a QGIS plugin should have its own repo. But I think this cloud-native geo querying of source.coop datasets could be much more accessible for users if there was a QGIS plugin that used the same technique.

I've never written one, but it would likely be a very cool first one to do, so if I have a chance I'll try it. But anyone else is welcome to try, and to reuse as much or as little code from here as desired.

[mtravis]

@cholmes I've got experience of creating a QGIS plugin and know others who could help so happy to work on this one with you.

[cholmes]

That'd be awesome! I have no idea where to even start, but if you get it going I'd be happy to contribute.

I don't have lots of qgis experience, but I like how Planet's plugin works - it's pretty easy to have a search by the current extent or to draw something and use that for the search. I struggled using qgis for my demo - tried like 5 minutes to make a new geojson layer with one feature that I could use for the query, so some short cuts in the plugin would be ideal.