Add site_name to example mkdocs.yml

[mattbostock]

site_name is a required field, so include it in the example.

[squidfunk]

The Material documentation states that you already have a working MkDocs project. It is not intended to fix you up with MkDocs. The docs clearly state:

Add the following line to your mkdocs.yml

site_name might end up being redundant in mkdocs.yml. We could add a notice in the Getting started guide, but no one ever complained about this, so I would favor to keep it short.

[mattbostock]

I misread that line to mean 'create an mkdocs.yml file with the following content', I guess because the pip package for Material pulls in mkdocs itself and I was following the README as a new user of Mkdocs (finding a good theme played an important part in my decision to use Mkdocs).

So feasibly you might follow the README as a new Mkdocs user and be confused why it complains about site_name (as I did).

That said I can understand that you don't wish to duplicate the documentation for Mkdocs.

[mattbostock]

Closed in favour of a smaller change:
#289