Draft: [US] layout variant us(cz_sk_de) was extended with Polish, Spanish, Finnish and Swedish

The new extended layout variant named us(cz_sk_pl_de_es_fi_sv) and is targeted to Czech and Slovak polyglots, like the original (Jirka's) one.

The proposed layout is the result of the discussion among Polyglot Gathering community of polyglots (https://www.polyglotgathering.com/).