Most of Polish characters are not being displayed in Vitashell's UI

[TheRadziu]

Hello,

Since current Polish translation is very outdated I've decided to update and translate it on my own, despite using VitaShell in English so far and from what've noticed vitashell does not properly display some of the polish characters, here is an example:

And here is how it should be displayed: "VitaShell w wersji %s jest już dostępny.\Czy chcesz zaktualizować tę aplikację?"

From list of polish characters (ą, ć, ę, ł, ń, ó, ś, ź, ż) only ł and ó are being properly displayed

Also, "Default" (string) is missing from language file (english_us.txt) so it cannot be properly translated (as seen on the screenshot, It still says "Default" under "theme"(Motyw graficzny) setting.

Cheers!