Automatically close all sidebars in all browser instances

[Saenil]

I think that it might be a good idea to automatically close all sidebars (in each browser instance) that have been opened previously, when user closes any of them.

I've had this problem just after installing the web extension, I had to close the sidebar 9 times. It's not a problem, just a small inconvenience.

P.S.
Great service btw ;)