Support for Cyrillic and Polish characters

[jmmelko]

Polish characters are not supported by the PNG renderer because the NotoSansCJK font was chosen for Western and Asian characters.

Most likely Cyrillic characters are not supported either.

This could be fixed by:

• adding a font (Czech is already supported by Western fonts I think)
• Loading it in Resources (permanently?)
• Choosing the font by detecting the song language. This is different from detecting the user web browser language…

[jmmelko]

Ok, I think this is fixed, excepted that diacritical marks are shifted rights with respect to base characters when rendered with PIL.
It seems that the fix is to use a library called raqm, but this requires a special installation step, and under windows to download an unofficial DLL and put in the same files as Python.exe:

python-pillow/Pillow#6258

this looks a bit overkill for supporting very rarely used languages.