Support some regional emoji flags

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Followup from #25 , it looks like there are a few other emoji flags that we don't support yet.

per https://en.wikipedia.org/wiki/Regional_indicator_symbol

A separate mechanism (emoji tag sequences) is used for regional flags, such as England 🏴󠁧󠁢󠁥󠁮󠁧󠁿, Scotland 🏴󠁧󠁢󠁳󠁣󠁴󠁿, Wales 🏴󠁧󠁢󠁷󠁬󠁳󠁿, Texas 🏴󠁵󠁳󠁴󠁸󠁿 or California 🏴󠁵󠁳󠁣󠁡󠁿.[12]

Country Coder doesn't have US States, but we could add support for England, Scotland, and Wales.

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I guess I added these flag overrides to location-conflation viewer a while ago, but it really makes more sense for them to live here in this project.
https://github.com/rapideditor/location-conflation/blob/a118790c6fe3d14d47d16cb7e025bf4742d691aa/docs/index.html#L399-L407

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I did this! 🎉
There is a different formula for converting an emoji tag sequence into a regional flag.
If more of these catch on, we can support them easily.

> coder.feature('🏴󠁧󠁢󠁳󠁣󠁴󠁿')?.properties.nameEn
'Scotland'
> coder.feature('🏴󠁧󠁢󠁥󠁮󠁧󠁿')?.properties.nameEn
'England'
> coder.feature('🏴󠁧󠁢󠁷󠁬󠁳󠁿')?.properties.nameEn
'Wales'

I also changed our handling of 'FX' re: #25 .
Before, we just followed the formula to return 🄵🅇 from the "enclosed alphanumeric supplement" unicode block.
Now we skip it, because we know that won't work. This allows country-coder to roll up to 'FR' which does show the French flag.