Added an option to change artist delimiter character

[azumukupoe]

As noted in the official ID3 tag documentation
https://id3.org/id3v2.3.0

TPE1
The 'Lead artist(s)/Lead performer(s)/Soloist(s)/Performing group' is used for the main artist(s). They are seperated with the "/" character.

[uuupah]

I feel like this should run through the config in the same way as the genre delimiter, different software respects different delimiters.