Extend project with continent, ISO codes, and ccTLD data and new methods

[sthiepaan]

As mentioned in #32 together with @bhatvikrant we decided to extend this package with:

• Information about continent that each country belong to
• Country ISO codes - numeric, Alpha-2 and Alpha-3 standard
• Country code Top-Level Domain (ccTLD)
• Area (will by done in Adding area field to data #40 by @amanpalariya)

For the project needs all new properties will be lowercase.

After adding all properties, each Country {Object} should contain:

{
  "country": "poland",
  "capital": "warsaw",
  "currency": "zloty",
  "native_language": ["polish"],
  "famous_for": "pierogi and potatoes",
  "phone_code": "+48",
  "flag": "https://flagpedia.net/data/flags/h80/pl.png",
  "drive_direction": "right",
  // NEW DATA
  "continent": "eu", // 1
  "iso": {  // 2
    "numeric": "616",
    "alpha_2": "pl",
    "alpha_3": "pol"
  },
  "tld": ".pl",  // 3
},

Additionally there will be new methods to use that data:

• getCountriesByContinent(continentName)
• getCountryDetailsByISO(isoType, isoValue)
• getCountryDetailsByDomain(domainName)