Pro component license verification doesn't work in incognito mode

[mvysny]

The issue might be caused by the Safari incognito mode that does not allow to use localStorage; Firefox also: any data put in Local or SessionStorage during a private browsing session will be lost as soon as the browser window is closed (intentionally or not).

Makes sense - when you close the porn window, everything should be gone - cookies, history, storage, etc.

However, would be great to have this documented at https://vaadin.com/docs/v14/bakeryflow/validating-license.html