make prominent link to the good msls.co/install-config-and-use/ page

It’s easy to miss how to configure the plugin. A link to the very useful page http://msls.co/install-config-and-use/ would be great in the FAQ as Q#1 and also in the Installation documentation. Two small changes that hopefully will result in much fewer questions/frustration.

https://wordpress.org/plugins/multisite-language-switcher/