[Wiki] Add screenshot for disabling isolation from toolbar icon

[r-a-y]

I wanted to add a new domain to a permanent container and forgot that you needed to have Isolation disabled before doing so.

I came across this wiki page: https://github.com/stoically/temporary-containers/wiki/Multi-Account-Containers-Isolation

And that page could benefit from having some screenshots to be a little bit clearer, especially when using the toolbar icon popup.

Here are some screenshots:

Thanks as always!