csrf added to startpage and first steps to double video

slaeforms/templates/startpage.html

@@ -11,6 +11,7 @@
         <div class="container">
     <h2>Hello! Thank you for participating in our study!</h2>
     <form action="http://localhost:5000/start" method="post">
+        <input type="hidden" name="csrf_token" value="{{ csrf_token() }}" />
     <label for="terms-and-conditions">
         <input class="inline" id="terms-and-conditions" type="checkbox" required name="terms-and-conditions" /> I accept the +terms and conditions</a>
     </label>