Add natural=wetland to a future version of the schema

[SomeoneElseOSM]

Currently 4 separate wetland values ("swamp", "bog", "string_bog", "wet_meadow") are written as a value of "kind" to the "land" layer.

Of the 4 million "natural=wetland", 59% have a wetland value (https://taginfo.openstreetmap.org/tags/natural=wetland#combinations ), leaving approx 1.5 million without, so that combination is very frequently used.

Usage of "natural=wetland" and "wetland" is spread evenly across the world; by inference usage of "natural=wetland" without "wetland" is too (https://taginfo.openstreetmap.org/tags/natural=wetland#map , https://taginfo.openstreetmap.org/keys/wetland#map ). it's not a value that is used more commonly by some OSM communities to express that concept than others.

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

The "land" layer is an obvious location, as a new value of "kind" - perhaps just "wetland"? This would include objects without the tag "wetland" and also objects with a value for "wetland" that was not one of "swamp", "bog", "string_bog", "wet_meadow".