add API docs for Pry::Config; fix pretty_print on Pry::Config.
add API docs for Pry::Config; fix pretty_print on Pry::Config.

[ci skip]

ooohiroyukiooo/pry,raeno/pry,printercu/pry,raeno/pry,printercu/pry,shockone/pry,geoffreylitt/pry,scalixte-mdsol/pry,icebreaker/pry,shockone/pry,gfvcastro/pry,ooohiroyukiooo/pry,icebreaker/pry,ngpestelos/pry,raeno/pry,nju520/pry,caporta/pry,nju520/pry,scalixte-mdsol/pry,pvdb/pry,nju520/pry,caporta/pry,ooohiroyukiooo/pry,geoffreylitt/pry,josue804/debunker,shockone/pry,bronzdoc/pry,josue804/debunker,jasnow/pry,jasnow/pry,gfvcastro/pry,pvdb/pry,bronzdoc/pry,scalixte-mdsol/pry,ngpestelos/pry,caporta/pry,jasnow/pry