Add OnScoreChange event
Add OnScoreChange event

For use in scrolling system on a later PR

peppy/osu,UselessToucan/osu,ppy/osu,peppy/osu-new,NeoAdonis/osu,peppy/osu,smoogipoo/osu,smoogipoo/osu,peppy/osu,smoogipoo/osu,UselessToucan/osu,ppy/osu,ppy/osu,UselessToucan/osu,smoogipooo/osu,NeoAdonis/osu,NeoAdonis/osu