[Website] Fix broken links!

[sbryngelson]

Citations/references are broken. e.g., https://mflowcode.github.io/documentation/md_visualization.html

Clicking the links to papers just gives a 404. Recommend replacing paper references with just a generic link to the references page.

[sbryngelson]

With this PR: #733

We now have a way to detect broken references like this automatically. This GH issue is to fix those broken links.