i18n(pl-PL): Add Polish translation

[SirRFI]

I am not a translator. As matter of fact, I prefer using English in computers. I made the translation based on context I found in the system ( https://github.com/pop-os/pop/issues/1975 ), though I haven't found some of these phrases anywhere. However, to ensure consistency with existing translations, I looked up to Fedora 35's GNOME 41 translations. Notable mentions:

• Dock = Dok
• Workspace = Obszar roboczy
• Top Bar = Górny pasek
• Hot Corner = Aktywny róg ("active corner")
• Applications = Programy ("programs", though "applications" => "aplikacje" is mostly used in phones)
• Workspaces Span Displays - Unsure what it is exactly, neither I managed to test it on a virtual machine. GNOME 41 has Workspaces on all displays = "Obszary robocze na wszystkich ekranach", so I went with that. If this thing works differently in PopOS, please show me how it works for proper translation.
• Launcher - I have not found such term being used. I am not aware of direct translation either, so as far I know it either goes untranslated or gets changed to something like "Panel startowy" ("start panel"). First I went with untranslated, but eventually decided to go with the "start panel".

I am also neither Rust or Linux DE developer. This is the first time I contribute to something related to both of these. One time I tried to run this on a virtual machine, I quickly found myself lacking some dependencies. As such, this contribution is untested.

Lastly, I am aware that Project Fluent is used. Never used it myself, so I am uncertain of how it works exactly. To my understanding after quick review - there are no magic keywords, just variables and switch-case like behavior. Let's take the dock's size translation as example:

size-large = Duży
size-medium = Średni
size-small = Mały

This was translated in masculine context, as "dok" reads like it's male. However, if you ever wished to reuse the translation for fonts, which are feminine, they would be as following: duża, średnia, mała. Third (undefined?) for would likely be: duże, średnie, małe.

Other example:

date-combo-center = Środek
date-combo-left = Lewa
date-combo-right = Prawa 

For date position this is good proper translation, like so: "left side" = "lewa strona". However, "go to left" would be "idź w lewo".

[jacobgkau]

Thank you for the translation. This did not build when it was opened (due to an unrelated issue) and is not currently building, and is based on an out-of-date version of desktop-widget at this point. I attempted to rebase it on master_jammy, but I do not have permission to push to @SirRFI's branch. I've opened a new PR containing this commit, which retains authorship information: https://github.com/pop-os/desktop-widget/pull/89

Closing this now since it's obsoleted.