[DOC] janitor.functions text on API docs is not a clickable link

[zbarry]

https://pyjanitor.readthedocs.io/reference/index.html

janitor.[biology,chemistry,finance] are.

[aopisco]

I would like to work on this

[ericmjl]

@aopisco hello from post-scipy! Hope you've been having a great time. I wanted to check-in with you to see if you'd like to submit a PR for this issue? If not, no worries! Just let us know - I'll release the issue back into the "available for hacking" pool. 😄

[aopisco]

@ericmjl please release the issue back! thanks!

[oriash93]

I would like to work on this, if possible.