Add Public Transport layer

[rustprooflabs]

Details

Ran into one example while working on #110.

See https://wiki.openstreetmap.org/wiki/Public_transport

[rustprooflabs]

This layer is affected by #2. Adding relations for public transport is missing 99% of the relations (101 / 102) that should be added.

SELECT ST_GeometryType(geom), COUNT(*)
    FROM osm.unitable
    WHERE tags->>'public_transport' IS NOT NULL
        AND geom_type = 'R'
    GROUP BY 1
;

st_geometrytype   |count|
------------------+-----+
ST_MultiLineString|  101|
ST_Polygon        |    1|