docs: add OpenSSF Best Practices registration badge

Author: hyperpolymath

README.md

@@ -1,4 +1,10 @@
+<!--
+SPDX-License-Identifier: MPL-2.0
+Copyright (c) Jonathan D.A. Jewell <j.d.a.jewell@open.ac.uk>
+-->
 # technical-notes
+[![OpenSSF Best Practices](https://img.shields.io/badge/OpenSSF-Best_Practices-green?logo=openssourcesecurity)](https://www.bestpractices.dev/en/projects/new?repo_url=https://github.com/hyperpolymath/technical-notes)
+
 
 Citable short technical notes and observations — AI accountability, agent
 behaviour, software engineering. Each note is archived on