Website update

[josherrickson]

I played around with altdoc and the friction was high enough that we can stick with pkgdown.

• [x] Update _pkgdown.yml to split functions into appropriate sections
• [x] Ensure internal functions are excluded

Blocking is:

• [x] Vignettes need to be working (#158)

[josherrickson]

The website is now building. Internal functions are removed. I took a first pass at organization, will probably need to revisit.

You can open /docs/dev/index.html to view it.

There's one vignette (covadj_with_clustering) which isn't building properly so this was excluded when I build the site; if you want to re-build it locally (with either make build_site or pkgdown::build_site()), temporarily delete that file first.

[jwasserman2]

@jwasserman2 look at categorization of functions in reference

[josherrickson]

Vignettes are good, so website is good to go.