make docs strict

[juliasloan25]

Is your feature request related to a problem? Please describe. When we update the docs, we could also consider making the doc creation "strict" - so that we get failures instead of warnings if a function or object can't be found, doesn't have a docstring, etc. We can't make this change before fixing all the broken links, but it may be good in the future to ensure we maintain high quality of our docs.

More info on the warnonly keyword can be found under the first bullet point here