QuGrid bundles third-party data files.

## MATPOWER case files

The files under `src/qugrid/cases/data/*.m` are unmodified test-case data
files from the MATPOWER project (https://matpower.org), redistributed under
the 3-clause BSD license reproduced in
`src/qugrid/cases/data/MATPOWER-LICENSE.txt`.

Copyright (c) 1996-2024, Power Systems Engineering Research Center (PSERC)
and individual contributors.

Individual case files carry their own provenance notes in their header
comments (for example, the IEEE 14-bus and 30-bus data originate from the
University of Washington power systems test case archive).
