Add docs on all available facades

[benfurfie]

This is a high level overview of the available facades, as suggested by @robdekort. It will eventually be used to link to documentation for each facade.

Structurally, it probably makes sense to have a small primer on what Facades are, link to the Laravel documentation to defer to that, and list the available facades (with a note that it’s currently being written out).

Links could be handled like the ‘Available Validation’ list on the Laravel docs (Laravel - The PHP Framework For Web Artisans).

[benfurfie]

I'll sort this one out this weekend.