Include constituent countries of the UK

[sarahmonster]

❤️ this library!

It might be nice to include the UK's constituent countries as well—I'm in Scotland and sometimes that distinction can be quite important!

🏴󠁧󠁢󠁳󠁣󠁴󠁿 Scotland (GB-SCT)
🏴󠁧󠁢󠁷󠁬󠁳󠁿 Wales (GB-CYM)
🏴󠁧󠁢󠁥󠁮󠁧󠁿 England (GB-ENG)
Northern Ireland (GB-NIR)

Northern Ireland is often classed as a province rather than a country, which may be why it's lacking its own emoji, but I know Wales only acquired their emoji relatively recently, so it may be in the works.

If you'd consider adding this to the library, I'd be happy to help facilitate as much as I can!