Added PL translations PO & MO

[jakubmieszczanin]

Hi @andris9

I have translated the messages into Polish.

[CLAassistant]

All committers have signed the CLA.

[andris9]

Thanks. In order to accept the PR you would need to accept the CLA agreement shown above.

I also added machine-translated translations for input validation messages. Maybe you would want to check if these seem OK: https://github.com/postalsys/joi-messages/blob/master/translations/pl.po - most of these messages are never shown but some are needed, for example hostname related etc (for example, if you try to use a non standard hostname for the IMAP hostname field when filling the hosted authentication form)

[jakubmieszczanin]

I signed the CLA and made a PR in the repository with translations of input validation messages - postalsys/joi-messages#5

[andris9]

Thanks! And I'll use your translations for joi-messages instead of the machine translated versions.

[andris9]

Seems to work