[credits] Add notes for the Polish translation (also: simplify notes taking in info.json)
This reflect the information transmited in ref: #160 (comment 744468) by @WorkingWarrior about the previous translation effort; even refactored it still deserve a note about the first attempt. I tried to wrap my head around the note taking system in info.json template with text and author; it is a nice system but a bit too complex for just adding a general note about the translation. I added a simple node in [credit] named [notes] where paragraph (ideally short lines) can be added to describe more accurately the big changes in the history of translation. This case is typical: a rewrite from scratch; and a attribution for the previous effort. TODO: makes the credit generator + the big table display this notes.