title: scala compile-type check for valid filepath?
body: <p>How do I create 'string type' that checks whether the file exists on some path at compile-time?
  e.g)</p>
  
  <pre><code>val spaceshipModelPath: ResourceFilePath(from="appRoot/assets") = "appRoot/assets/spaceshipModel.obj"
  </code></pre>
  
  <p>or:</p>
  
  <pre><code>type ObjResourcePathType = ResourceFilePath["appRoot/assets", ".obj"]
  val spaceshipModelPath: ObjResourcePathType = ...
  </code></pre>