Support YAML changelog definitions

[codebymikey]

Given that YAML is a superset of JSON, using a YAML parser would ensure that existing JSON functionality is kept while allowing support for YAML's more advanced and human friendly features like inline comments, easier multiline entries, special characters, anchors etc.

It'd essentially allow users to define their changelog like:

{
  "extra": {
    "changelog": {
      "source": "changelog.json"
    }
  }
}

or

{
  "extra": {
    "changelog": {
      "source": "changelog.yml"
    }
  }
}

The PECL YAML extension should be preferably used if it's available, as it's more performant than third party libraries like symfony/yaml. However if the extension is unavailable, then the plugin should fallback to the third party library.

This should not result in a breaking change in the existing behaviour.

Is this a feature the plugin is willing to accommodate in the future?