Add 'something wrong with this site?' form for each city

[eeeschwartz]

Where people could report data errors and whatever else (inspired by gov.uk like everything else we do).

Use a city administrator email in cities.geojson to send the feedback to.

[bigfleet]

Technical contact would also be helpful: (See #162)

[bigfleet]

See #203 as well. When that's available, this can be closed by adding a contact form that notifies that person.