Add welcome page (#302)

Add welcome page for A/B testing

VAN-514

src/data/constants.js

@@ -2,6 +2,7 @@
 export const LOGIN_PAGE = '/login';
 export const REGISTER_PAGE = '/register';
 export const RESET_PAGE = '/reset';
+export const WELCOME_PAGE = '/welcome';
 export const DEFAULT_REDIRECT_URL = '/dashboard';
 export const PASSWORD_RESET_CONFIRM = '/password_reset_confirm/:token/';
 export const PAGE_NOT_FOUND = '/notfound';