code: function add(locales, rule) {
    var i;
  
    rule.c = rule.c ? rule.c.map(unpack) : [ 'other' ];
    rule.o = rule.o ? rule.o.map(unpack) : [ 'other' ];
  
    for (i = 0; i < locales.length; i++) {
      s[locales[i]] = rule;
    }
  }
docs: adds given `rule` pluralizer for given `locales` into `storage`