title: docker-compose adding to PATH
body: <p>I need to add some paths to my PATH in docker-compose.yml</p>
  
  <p>in docker-compose.yml I have tried</p>
  
  <pre><code>app:
      ...
      environment:
          - PATH /code/project
  </code></pre>
  
  <p>however that just overwrites the existing PATH - whereas I want to add to the existing PATH</p>