fix inverted sub/superscript shortcuts (#720)
fix inverted sub/superscript shortcuts (#720)

ospalh/libanki3,Stvad/anki,jakesyl/ruby-card,kenjhim/anki,holycrepe/anki,xuewenfei/anki,go38/anki,LucasCabello/anki,subfusc/anki,jkitching/anki,florianjacob/anki,weihautin/anki,abeyer/anki,Arthaey/anki,hssm/anki,jakesyl/ruby-card,socialpercon/anki-1,eduOS/anki,weihautin/anki,hssm/anki,sunclx/anki