Cookie lifespan

[DiFuks]

Currently, when choosing cookie storage, it is not possible to control its lifespan, which causes the theme cookie to reset after restarting the browser

It might be worth adding an option to set the cookie lifespan or, by default, setting the maximum lifespan

[atinux]

Happy to open a PR for it?

[tasiotas]

#301 adds cookieAttribs that lets you specify expires and others