endonyms: add endonyms dictionary for region placetype

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as mentioned in https://github.com/pelias/api/issues/1629, the work in https://github.com/pelias/wof-admin-lookup/pull/314 covered country and megacity endonyms but didn't cover the region placetype.

I've just landed https://github.com/pelias/wof-admin-lookup/pull/316 in order to update the existing dictionaries and then added a new dictionary for the region placetype here.

This work requires testing as per https://github.com/pelias/wof-admin-lookup/pull/314, there is a concern that it will adversely impact the index size, although that remains to be seen.

resolves: https://github.com/pelias/api/issues/1629

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Tagged and released as pelias-wof-admin-lookup@7.10.0