Installing drupal 8 distribution on pantheon

[ugintl]

I have downloaded a drupal 8 distribution using composer and as usual, the vendor folder is outside the docroot folder. How can I make it work on pantheon? My composer file is attached. composer.json.txt

This is the project https://www.drupal.org/project/openy I used the composer template provided by them on github https://github.com/ymcatwincities/openy-project