Add documentation for the usage of the import function

src/main/resources/templates/course/create/participant.html

@@ -83,6 +83,12 @@
                             Assistants/Managers/Teachers</button>
                     </div>
                 </div>
+                <div class="col-sm-8">
+                    The csv should look like: <br>
+                    "netid1","role1" <br>
+                    "netid2",role2" <br>
+                    The following roles can be applied: <i>ta, assistant, manager, teacher</i>
+                </div>
             </form>
         </div>
 </section>