i18n: Add Polish translation

Signed-off-by: Marcin Mikołajczak <me@m4sk.in>
4 jobs from master in 4 minutes and 2 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Prepare
passed #370
setup-test-env

01:07

 
  Review
passed #373
eslint

00:59

passed #372
i18n-tasks

00:55

passed #371
rubocop

01:00