Add rendering for emergency=emergency_ward_entrance

[kocio-pl]

Related to #2938.

This tag has not too much use, but it's documented and climbing (currently 361 uses):

https://wiki.openstreetmap.org/wiki/Tag%3Aemergency%3Demergency_ward_entrance

Might be rendered as https://github.com/gravitystorm/openstreetmap-carto/blob/master/symbols/entrance.10.svg (maybe mirrored to make it easier to recognize) in healthcare color.

[matkoniecz]

I think that 361 is far too low to render it.

[kocio-pl]

Closing for now, but I hope the usage will get higher eventually.

[jeisenbe]

959 uses now - still rare. Let's reconsider later.