heroku.yml now supports app creation and manifest generation

Change effective on 28 June 2018

You can now create applications from a heroku.yml manifest, and create a manifest from an existing application.

To enable these features, switch to the beta CLI channel and install the manifest CLI plugin:

$ heroku update beta
$ heroku plugins:install @heroku-cli/plugin-manifest

To create a manifest from an existing app:

$ heroku manifest:create

To create an application from a manifest in the current directory:

$ heroku create --manifest

See the documentation for more information.