Update README with formatters in the extend section.
Update README with formatters in the extend section.

zongkelong/rivets,altmind/rivets,jccazeaux/rivets,GerHobbelt/rivets,moneyadviceservice/rivets,altmind/rivets,mikeric/rivets,zongkelong/rivets,benderTheCrime/tiny-rivets,zongkelong/rivets,GerHobbelt/rivets,altmind/rivets,re-clone/rivets,GerHobbelt/rivets,nopnop/rivets,QAPInt/rivets,jccazeaux/rivets,jccazeaux/rivets,MishaMykhalyuk/rivets,QAPInt/rivets,QAPInt/rivets,npmcomponent/mikeric-rivets,re-clone/rivets,MishaMykhalyuk/rivets,re-clone/rivets,kangax/rivets,nopnop/rivets,MishaMykhalyuk/rivets,nopnop/rivets,mikeric/rivets,mikeric/rivets