fixes #74
`

• create a new folder src/routes/api/submissions

  • create an index.ts file which'll act as the url map
  • create an controller.ts file which'll export an object containing the handler
  • mount /api/submissions/:id endpoint to the polling controller

• write test for the api

  • Test if the API fives 403 if the api key is not provided or incorrect
  • Test if the API gives 404 if submission id not found
  • Test if the API gives returns the serialized submission model
  • update the test here and here

`