Enhancement: print the source event, output data or event in JSON instead of plain text format

`--listen` and `--tail` print events in a human-readable format. I want the json, to parse it easily in my script. Could matrix-commander print the json by default or with a command-line flag?

Look at the code handling the --listen and --tail commands, likely in the main command-line interface module. Identify where events are formatted for output. Add a flag to output raw JSON. Test by running the tool with the new flag and verifying JSON output is parseable.

索引モデルが issue の本文から書いたものです。