add %j as an alias for %O

[chocolateboy]

same as util.format and many other implementations:

package	char	conversion	notes
extsprintf	%j	util.inspect
lodash-decipher	%j	JSON.stringify	no width/precision
s	%j	JSON.stringify	only supports %d and %j
sprintf.js	%j	JSON.stringify	contaminates the global scope and String
string-kit	%J	JSON.stringify
tea-sprintf	%j	JSON.stringify	no width/precision