Guide: add a new city

To add a new city or location, changes have to be made to both the front and back end:

In datablue

1. Add the location's geocoordinates and if available, the wikidata QID of the fountain operator catalog. see commit
2. Add location as allowable value in API endpoints. see commit

In proximap

1. Add location as a valid url parameter, include aliases. see commit
2. Add translations for location name. see commit