Add amenity=taxi to a future version of the schema

[SomeoneElseOSM]

Currently at https://taginfo.openstreetmap.org/keys/amenity#values there are 50k of these worldwide, so it's a frequently used value. Usage is spread evenly across the world https://taginfo.openstreetmap.org/tags/amenity=taxi#map ; it's not a value that is used more commonly by some OSM communities to express that concept than others. It's documented at https://wiki.openstreetmap.org/wiki/Tag%3Aamenity%3Dtaxi .

It would add value to a general purpose map style that may want to use the Shortbread schema.

It would make sense to add it to: https://shortbread-tiles.org/schema/1.1/#layer-public_transport

to mirror the way that highway=bus_stop et. al. handled.