Doxygen Link Broken on ReadTheDocs

[kab163]

Describe the bug

The doxygen link in the ReadTheDocs does not have a link to any doxygen. The docs are not being generated I don't think. https://umpire.readthedocs.io/en/develop/doxygen/html/index.html

To Reproduce

Go to https://umpire.readthedocs.io/en/develop/doxygen/html/index.html

Expected behavior

Docs work!

Additional context

I think it may be an issue with breathe module not showing up in sphinx or something. But either way, this needs to be fixed