test: add e2e test for submission happy path

Simple click through of the submission form in its current state.

Mostly here just to get people used to the idea of writing and updating these tests as we develop further.

app/components/dashboard/Dashboard.js

 import React from 'react'
-import { Link } from 'react-router-dom'
+import ButtonLink from '../ui/atoms/ButtonLink'
 
 const Dashboard = () => (
   <div>
     <h1>Dashboard Dummy Page</h1>
-    <Link to="/submit">Submit a manuscript</Link>
-    <div>
-      <Link to="/manuscript">View manuscript</Link>
-    </div>
+    <ButtonLink data-test-id="submit" primary to="/submit">
+      Submit a manuscript
+    </ButtonLink>
   </div>
 )