Fix website formatting

[kaitejohnson]

Problem
Website theme isn't rendering properly, missing some components of navigation bar, etc

Additional context
We haven't set up families of functions in the package yet, nor do we have more articles beyond the baselinenowcast.Rmd which will fall into the Getting Started vignette, so I won't include the larger Reference structure yet, and will exclude the articles section on the navigation bar for now.

[seabbs]

We haven't set up families of functions in the package yet, nor do we have more articles beyond the baselinenowcast.Rmd which will fall into the Getting Started vignette, so I won't include the larger Reference structure yet, and will exclude the articles section on the navigation bar for now.

Is there an issue for this? Sorry I had missed this wasn't in scope

[kaitejohnson]

#25