Add Polish to document languages

[eikek]

Original request: #488 (comment)

In order to recognize dates, I need the Polish date pattern(s) used in documents. I also need spelled out month names. Here are two issues for other languages as an example: #948 and #679

[eikek]

Hi @maciekb since you opened the original request: may I ask you for some information? I would need

• Polish date patterns that are used most on documents
• Polish month names

Thanks!

[mimek]

Hi @eikek ,
https://www.localeplanet.com/icu/pl-PL/index.html

Most used polish date patterns are Date.3 and Date.1 (second one quite rarely).
Polish months names are also there.

Thanks for all the job!