Place machine-readable output as a file

[riywo]

High level commands such as web test run use stdout for informing to the human user. Therefore, it is not easy to pass the re-usable data to other process via pipe.

We could use stderr for logging and stdout for machine-readable information but such convention will break easily. Also, machine-readable information is not needed for human.

Thus, we should put such data on data directory like ~/.data/autify/output/web-test-run-<timestamp>-<pid>.json then print the location as a log. The other process like CI/CD integration can parse the file location from log easily and get the output in json format.

[riywo]

Or, providing a new option like --output-file=<file> might be better.