i18n: Add Polish translation

Signed-off-by: Marcin Mikołajczak <me@m4sk.in>
4 jobs from master in 4 minutes and 6 seconds (queued for 30 seconds)
Status Job ID Name Coverage
  Prepare
passed #377
setup-test-env

01:05

 
  Review
passed #380
eslint

01:01

passed #379
i18n-tasks

00:58

passed #378
rubocop

01:00