Feature: option to build geojson map layer from list of location grid.

[chrisbc]

We need a python function to produce a geojson polygon layer (for hazard maps) from a given list of locations (which will be one of our gridded regions.)

This will be an optional feature see https://stackoverflow.com/questions/68790441/python-poetry-install-optional-dependencies

• installs dependencies when user specifies nzshm-common[geometry]
• hexagon cells for gridded hazard mesh (see https://gis.stackexchange.com/questions/341218/creating-a-hexagonal-grid-of-regular-hexagons-of-definite-area-anywhere-on-the-g )
• square cells for gridded hazard mesh
• circular shapes with radius (n km) as per solvis library