[BUG] Limit latin name extraction to valid language codes with no non-latin characters about planetiler

[SomeoneElseOSM]

Just in case people aren't aware of it, I'll throw in the canonical example where "odd" language codes are used that are in some sense correct: https://www.openstreetmap.org/node/267762522 . There name:en_GB and name:en_IE are used to show the different names used by different communities - the https://buseireann.ie/ bus that goes there definitely only has "Derry" and "Doire" on the front!

Whether this is something that this repository ought to worry about is a different question of course - I just thought it might be useful to mention one of the edge cases.

[1ec5]

What makes name:en_GB and name:en_IE odd is not the country codes but rather the underscores. To the extent that name subkeys should be valid IETF language tags, these keys should be name:en-GB and name:en-IE, respectively.