placeholder for "Apps"

[cambro]

Please add a placeholder for "Apps" in the top navigation link (after "API"). This will link to a separate page "Applications," with same general format as https://xdd.wisc.edu/about.html

Once this is in as a placeholder I will modify the content of the apps.html file.

[iross]

Added a stub over on a dev/apps branch. There's instructions in the README on doing a docker deployment on your local machine to see changes.