Add documentation on rivets.init.
Add documentation on rivets.init.

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