Change seeders implementation, fix Russia relationship with its cities and add all Morocco' cities.

[mednasserallah]

Change array() function to short array syntax ([]) in the following seeders for less code and to make things easy to maintenance.

• database/seeds/WorldCitiesTableSeeder.php
• database/seeds/WorldContinentsTableSeeder.php
• database/seeds/WorldCountriesTableSeeder.php

Also, I grouped cities by their countries, and countries by the continents.
Make more sense in case someone wants to search for certain country to add some missing cities instead of check the country ID and then search by ID.

Fix Russia (country) relationship with its cities

>>> use Khsing\World\World;
>>> World::getByCode('ru')->cities->pluck('name')
=> Illuminate\Support\Collection {#3072
     all: [ 
        "Abakan", "Aginskoye", "Anadyr", "Arkhangelsk", "Astrakhan", "Barnaul", "Belgorod", "Birobidzan", 
        "Blagoveshchensk", "Bryansk", "Chabarovsk", "Cheboksary", "Chelyabinsk", "Cherkessk", "Chita", 
        "Elista", "Gorno-Altajsk", "Grozny", "Irkutsk", "Ivanovo", "Izhevsk", "Jakutsk", "Jaroslavl", 
        "Jekaterinburg", "Juzno-Sachalinsk", "Kaliningrad", "Kaluga", "Kazan", "Kemerovo", "Khanty-Mansiysk", 
        "Kirov", "Kostroma", "Krasnodar", "Krasnojarsk", "Kudymkar", "Kurgan", "Kursk", "Kyzyl", "Lipeck", "Magadan", 
        "Magas", "Makhachkala", "Maykop", "Moscow", "Murmansk", "Nalchik", "Naryan-Mar", "Niznij Novgorod", 
        "Novosibirsk", "Omsk", "Orel", "Orenburg", "Palana", "Penza", "Perm", "Petropavlovsk-Kamchatskiy", "Petrozavodsk", 
        "Pskov", "Rostov-na-Donu", "Ryazan", "Salekhard", "Samara", "Saransk", "Saratov", "Smolensk", "St. Peterburg", 
        "Stavropol", "Syktyvkar", "Tambov", "Tomsk", "Tula", "Tver", "Tyumen", "Ufa", "Ulan-Ude", "Uljanovsk", "Ust-Ordynsky", 
        "Velikij Novgorod", "Vladikavkaz", "Vladimir", "Vladivostok", "Volgograd", "Vologda", "Voronezh", "Yoshkar-Ola",
     ],
   }

Add all Morocco' cities

>>> use Khsing\World\World;
>>> World::getByCode('ma')->cities->pluck('name');
=> Illuminate\Support\Collection {#3045
     all: [ 
        "Agadir", "Aït Melloul", "Al Hoceima", "Azrou", "Beni Mellal", "Benslimane", "Berkane", "Berrechid", "Bouskoura", 
        "Casablanca", "Dar Bouazza", "Dcheira El Jihadia", "El Jadida", "El Kelaa Des Sraghna", "Errachidia", "Essaouira", 
        "Fes", "Fquih Ben Salah", "Guelmim", "Ifrane", "Inezgane", "Kenitra", "Khemisset", "Khenifra", "Khouribga", 
        "Ksar El Kebir", "Larache", "Marrakech", "Meknes", "Mohammedia", "Nador", "Ouarzazate", "Oued Zem", "Oujda", "Rabat", 
        "Safi", "Salé", "Sefrou", "Settat", "Sidi Bennour", "Sidi Kacem", "Sidi Slimane", "Tan-Tan", "Tangier", "Taourirt", 
        "Taroudant", "Taza", "Temara", "Tetouan", "Tiznit", "Western Sahara",
     ],
   }

[khsing]

great, thx