Update cities.json

The following cities (32) have been added to the metroextractor system:

AFRICA //

+ Accra, Ghana 
+ Bamako, Mali 
+ Conakry, Guinea 
+ Cotonou, Bénin 
+ Durban, South Africa 
+ Kano, Nigeria 
+ Khartoum, Republic of Sudan 
+ Lomé, Togo 
+ Luanda, Angola 
+ Monrovia, Liberia 
+ Niamey, Niger 
+ Ouagadougou, Burkina Faso 
+ Yamoussoukro, Ivory coast 

ASIA //

+ Ho Chi Minh City, Vietnam 
+ Kota Kinabalu, Malaysia 
+ Phnom Penh, Cambodia 
+ Vientiane, Laos 

SOUTH AMERICA //

+ Guayaquil, Ecuador 

NORTHERN EUROPE //

+ Aarhus, Denmark 
+ Bergen, Norway 

EASTERN EUROPE //

+ Vilnius, Lithuania 

WESTERN EUROPE //

+ Dublin, Ireland 

NORTH AMERICA //

+ Des Moines, Iowa 
+ Oklahoma City, Oklahoma 
+ Omaha, Nebraska 
+ Puebla, Mexico 
+ Rimouski, Canada 
+ Saguenay, Canada 
+ Santa Fe, New Mexico 
+ Shawinigan, Canada 
+ Sherbrooke, Canada 
+ Trois-Rivieres, Canada
Update cities.json