Add different output formats about i18n-command

[swissspidy]

I was wondering if I could just extend WP_CLI\Loggers\Base for this and call set_logger() to keep it simple. 🤔

[swissspidy]

For my own use case it would be awesome if I could get something like this at the end:

{
  "source": "/path/to/foo-plugin/",
  "mainFile": "/path/to/foo-plugin/foo-plugin.php",
  "textdomain": "foo-plugin",
  "mergedWith": "/path/to/foo-plugin/languages/js-strings.pot",
  "destination": "/path/to/foo-plugin/languages/foo-plugin.pot",
  "extractedStrings": 127,
  "warnings": [
    {
      "type": "invalid-comment",
      "file": "/path/to/foo-plugin/src/some-file.php",
      "line": 123
    },
    {
      "type": "invalid-comment",
      "file": "/path/to/foo-plugin/src/some-file.php",
      "line": 410
    },
    {
      "type": "invalid-domain",
      "file": "/path/to/foo-plugin/src/another-file.php",
      "line": 10
    }
  ]
}