Add a support index page

Our support process is about to get more fully fledged so we’ll need
an index page to route people properly.

We reckon that users will also want to know what the support process is,
so let’s explain it on this page.

tests/app/main/views/test_feedback.py

@@ -19,6 +19,11 @@ def test_logged_in_user_redirects_to_choose_service(app_,
             assert response.location == url_for('main.choose_service', _external=True)
 
 
+def test_get_support_index_page(client):
+    resp = client.get(url_for('main.support'))
+    assert resp.status_code == 200
+
+
 def test_get_feedback_page(app_):
     with app_.test_request_context():
         with app_.test_client() as client: