Add the character splitter

[Moebytes]

We already implemented a character splitter to generate character notes and tag groups over here:

https://github.com/Moestash/moepics-scripts/blob/main/charactersplit/charactersplit.py

Maybe we should migrate this over to the main site. A change will need to be made to the OCR function, which replaces all notes.
OCR - replaces all notes other than character notes
Character splitter - replaces only character notes

I don't want to run tag updates directly from here, so instead it will just show a textbox with the generated tag groups that you can copy and paste into the tag edit dialog.