chore: add currency information and local names to country list

[abdullahceylan]

This PR enhances the country list by adding comprehensive currency information and local names for all countries. The additions include:

• Local names in native languages/scripts (solves Add country name with local language #12)
• Currency names
• Currency codes (ISO 4217)
• Currency symbols

Changes Made

• Updated CountryInterface type to include new optional fields:

  • currency?: string - Full currency name
  • currency_code?: string - ISO 4217 currency code
  • currency_symbol?: string - Currency symbol

• Added currency information for all countries

• Fixed corrupted flag emojis for several countries

• Updated local names to be more accurate and include native scripts

• Standardized currency symbol formats

Sources

• Currency information: https://www.xe.com/en-gb/symbols
• Local names: https://worldpopulationreview.com/country-rankings/names-of-countries-in-their-own-language

[Skarvion]

I'm not the maintainer, but looking at this, there are few feedbacks:

• It will be great if the data can work with https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/NumberFormat, but we'll need the locale information which we don't have
• Probably worth adding a test case that ensure the currency format in the data.ts is the same with the Intl.NumberFormat content

Cheers for the PR!

[necessarylion]

Thanks a bunch for the PR! It looks great to me.

By the way, could you please add the newly added keys function to the src/country.ts file?

Also, make sure you have a cover test case for it. Thanks again!