title: Create fresh Rails 5 credentials on clone
body: <p><strong>Problem</strong>
  I am creating a <a href="https://github.com/mklemme/rails-template" rel="noreferrer">rails 5.2 template</a>. I've created a new project which is a <a href="https://github.com/invisible-hats/gra-app" rel="noreferrer">fork</a> of the template. I don't want to use the same <code>config/master.key</code> since this would be shared across <code>X</code> other projects. Is there a way to generate a new key &amp; <code>config/credentials.yml.enc</code> pair? That way I could include a <code>config/credentials.yml.enc.sample</code> and they run <code>rails credentials:new</code> or something then copy the contents over?</p>
  
  <p>Can't find anything in the documentation or google/so searches about this and my alternative is to use the same key across all my public projects :,(</p>