Enhance country data with currency, time zone, and flag support

[selfmadecode]

We can improve this package by extending the country data to include:

Currency information
Time zone(s)
Country flag (e.g., ISO code, emoji, or asset URL)

At the same time, we should consider users who only need basic country information (such as country names) without additional metadata. To support these use cases, we should allow consumers to request only the required fields, ensuring we do not serve unnecessary or excess data.