Add new bats tests and new json file

This merge request is for fixing a bug in the subcommand convert. The bug occurs when converting a dictionary read from the stdin to a dictionary in the json format: instead of properly writing the name of the converted file in the id field, it writes "stdin". A new file and a new bats test have been added to showcase this bug: ../sample/json/028_person.json and in ../bats/test_dico_convert_json.bats.