Add locale for fi-FI

[gothenburgbitfactory]

Add locale for fi-FI

[anttiheinonen]

Not sure about the ultimate official source, but https://almanakka.helsinki.fi/en/flag-days-and-holidays-in-finland.html is definately a very reputable one.
All the finnish translations can be found from https://almanakka.helsinki.fi/fi/liputus-ja-juhlapaivat/suomen-kalenterin-juhlapaivat.html, your list looks good to me.

[lauft]

Thank you for your input!

I have updated the fi-FI locale and it reproduces the available holidata from 2011 to 2018, so it's good to publish. The missing legal sources is a bit dissapointing; the wiki page lists Vuosilomalain 4 § as a source, but I could not find a distinct listing of holidays there - maybe later then.

From the data I also created the Swedish version (sv-FI) as well. 🐦🐦 + 🥌