Duplicated files in composite tutorials pages

[ms609]

In https://revbayes.github.io/tutorials/divrate/branch_specific.html (and other tutorials), the "Data files and scripts" box lists the same file multiple times, and in multiple places (under "Data files" and "Other").

Presumably a component of the issue is that the main page is built from multiple modules.

It would be nice (if a low priority?) to:

• check for duplicate file names
• if file contents are identical (as here), print the link only once
• if file contents differ, flag with a warning.