The javascript libraries should be installed in the `libs` directory.
Either make a `libs` directory here or a symbolic link to somewhere else.

Currently, libs should contain:

    bootstrap-4.1.3
    codemirror-5.42.0
    DataTables
    fontawesome-free-5.6.1-web
    MathJax-2.7.5

and the files:

    jquery-3.3.1.min.js
    popper.min.js

The DataTables directory was generated by https://www.datatables.net/download/
Select:
- styling: bootstrap4
- packages: datatables
- extensions: responsive
This will generate a zip that contains the directory `DataTables`. Expand the zip into `libs`.