add link to docs

[cmungall]

there are docs but they are secret

https://monarch-initiative.github.io/monarchr/articles/monarchr

the actual link on the readme is broken

[oneilsh]

I think I see - the links are working on the github readme, but not on the published docs page.

@bschilder, on the latter the links are coming through like https://`r%20owner`.github.io/%60r%20pkg%60 - at which point do those get rendered in the workflow?