Update cities.json

30 new cities added: 

North America //
Charlottetown, Fredericton, Halifax, Hamilton, Iqaluit, Kingston, La Habana, Mississauga, Québec, Regina, St. John's, Whitehorse, Winnipeg, Yellowknife

Africa //
Abidjan, Alexandria, Antananarivo, Bangui, Casablanca, Lilongwe, Lusaka, Maputo, Tunis

South America //
Asuncion, Montevideo

Asia //
Pune

Western Europe //
Basel, Bern, Geneva, Lausanne

First time I'm contributing to the file, let me know if everything's fine.

S.