German Leters not working in Song Search

[LoZe]

I noticed that the letters Ä, Ö, Ü, and ß don’t work in the song search.
So I can't search for bands like "Die Ärzte" or "Böhse Onkelz".
I think the IsAlphaNumericChar() function doesn’t include these letters.

https://github.com/ultrastares/ultrastar-worldparty/blob/556539dfbdee70416071982f83246c8185159bcd/src/screens/UScreenSongMenu.pas#L115C6-L115C18