Add greek cities geo data

[tsevdos]

We can get data from this site: https://geodata.gov.gr

[arisGio]

Visiting https://geodata.gov.gr/dataset/poleis & choosing GeoJson && WSG format is the most suitable resource for this open issue.

[tsevdos]

Let's add the below helper fns for the cities:

getCities({ locale = "el" }: options) => City[]
searchCityByName({searchTerm: "Αθήνα", locale? = "el"}: options) => City[]
getCityById({ id, locale = "el" }: options) => City
getCityAdministrativeDivision({ id, locale = "el", type: "region" | "unit" | "municipality" | "prefecture" }: options) => Region | Unit | Municipality | Prefecture | null

[tsevdos]

fixed with #83