fix typo in readme
fix typo in readme

opyate/joi,thethanghn/react-native-joi,pikselpalette/joi,tpiecora/joi,pandeysoni/joi,jeffbski/joi,danielb2/joi,myndzi/joi,bananaoomarang/joi,geminiyellow/joi,cesarmarinhorj/joi,jagoda/joi,olistic/joi-extended,lloydbenson/joi,ck-lee/joi,rmoorman/joi,davidbenko9/joi,robertherber/joi-extended,myndzi/joi,naitsric/joi