docs: add OpenSSF Best Practices registration badge

Author: hyperpolymath

README.adoc

@@ -1,5 +1,8 @@
 // SPDX-License-Identifier: MPL-2.0
+// Copyright (c) Jonathan D.A. Jewell <j.d.a.jewell@open.ac.uk>
 = nesy-solver
+image:https://img.shields.io/badge/OpenSSF-Best_Practices-green?logo=openssourcesecurity[OpenSSF Best Practices,link="https://www.bestpractices.dev/en/projects/new?repo_url=https://github.com/hyperpolymath/nesy-solver"]
+
 Jonathan D.A. Jewell <j.d.a.jewell@open.ac.uk>
 :toc:
 :toc-placement: preamble
@@ -45,4 +48,6 @@ pipeline:
 
 == License
 
-MPL-2.0. See link:LICENSE[LICENSE].
+This project is licensed under the Mozilla Public License, v. 2.0. See the `LICENSE` file for details.
+
+SPDX-License-Identifier: MPL-2.0