fix 'good first issue' link in readme
fix 'good first issue' link in readme

UselessToucan/osu,peppy/osu-new,ppy/osu,peppy/osu,smoogipoo/osu,NeoAdonis/osu,smoogipoo/osu,UselessToucan/osu,smoogipoo/osu,EVAST9919/osu,smoogipooo/osu,peppy/osu,peppy/osu,EVAST9919/osu,ppy/osu,UselessToucan/osu,NeoAdonis/osu,NeoAdonis/osu,ppy/osu