Added credits to README
Added credits to README

matejlauko/floppybird,ajrulez/floppybird,EmanuelKuhn/papflappybird,armikhael/flappy-key,wanderingstan/handybird,corywalker/floppybird,rukmal/FlappyLeapBird,liuhong1happy/floppybird,cmsc471-swagbag/floppybird,Kkevsterrr/ashtonbird,Kkevsterrr/ashtonbird,CallaJun/flappyeddie,liuhong1happy/floppybird,rukmal/FlappyLeapBird,nebez/floppybird,corywalker/floppybird,EmanuelKuhn/papflappybird,CallaJun/flappyeddie,RedWhiteMiko/floppybird,wanderingstan/handybird,ajrulez/floppybird,matejlauko/floppybird,RedWhiteMiko/floppybird,nebez/floppybird,cmsc471-swagbag/floppybird