Add index links

[ConfidantCommunications]

Because the built-in menu system for the OpenFL documentation makes the left-column menu header for "Tutorials" only expand the sub-menu options, preventing a link, users can easily overlook the fact that there is a lengthy list of tutorials on the index page. Adding this link at the top of the subpages may help users find their way to the further documentation. I brought this up a few months ago here.

[ConfidantCommunications]

Any thoughts on this? Should I be submitting documentation changes?