Add Elm adapter

[soanvig]

I guess there is not very much use for it, but Elm is interesting (though not released for 2 years) framework, and JSR v1 was mentioned in

Elm in Action

https://books.google.pl/books?id=rHbgDwAAQBAJ&pg=PA131&lpg=PA131&dq=mateusz+koteja&s[…]Q&hl=pl&sa=X&ved=2ahUKEwjIiNia7OP1AhXPtYsKHZ3-ACcQ6AF6BAhFEAM