troubleshooting added to faq for issue #367

Not entirely sure about direction or format wanted. But heres a few additions, willing to re-write as needed.
I'd remove the description about how to install a package - after all they installed qutebrowser in some way ;)

Instead it might make sense to describe this is just a workaround for a bug fixed in Qt 5.4, and link to https://bugreports.qt-project.org/browse/QTBUG-41360 and/or https://bugs.webkit.org/show_bug.cgi?id=119951