Add carolinamatdb.org

Originally posted by @ml-evs at Materials-Consortia/OPTIMADE#124

README.md

@@ -61,6 +61,7 @@ Contributions are very welcome - please follow the [guidelines](CONTRIBUTING.md)
 - [ATB](http://compbio.biosci.uq.edu.au/atb) - Automated Topology Builder and Repository.
 - [AtomWork](https://crystdb.nims.go.jp/en) and [AtomWork-Adv](https://atomwork-adv.nims.go.jp) - Data platform of NIMS, Japan (based on the PAULING FILE experimental database).
 - [Baikov Institute of Metallurgy and Materials Science](http://bg.imet-db.ru) - Russian databases.
+- [Carolina Materials Database](http://www.carolinamatdb.org) - an ML-DFT database of the University of South Carolina.
 - [CascadesDB](https://cascadesdb.org) - Molecular dynamics simulations of collision cascades, by the International Atomic Energy Agency.
 - [Catalysis Hub](https://www.catalysis-hub.org/) - Web-platform for sharing data and software for computational catalysis research.
 - [cccbdb](http://cccbdb.nist.gov) - Computational Chemistry Comparison and Benchmark Database.