Version 0.6.0 drops the bundled support for prh because there is now a standalone package for it. If you miss the validation feature, please install "prh" extension.
and all the subsequent dependencies are packaged in the extension too.
Other projects
https://github.com/erukiti/ya-language-review also provides Re:VIEW preview and diagnostic features. It runs review locally (while my extension is based on review.js) so you can get the very latest features, in case you need them.