docs: add OpenSSF Best Practices registration badge

Author: hyperpolymath

README.adoc

@@ -1,6 +1,10 @@
+// SPDX-License-Identifier: MPL-2.0
+// Copyright (c) Jonathan D.A. Jewell <j.d.a.jewell@open.ac.uk>
 = Sanctify-PHP
+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/sanctify-php"]
 
-image:https://img.shields.io/badge/License-PMPL--1.0-blue.svg[License: PMPL-1.0,link="https://github.com/hyperpolymath/palimpsest-license"]
+
+image:https://img.shields.io/badge/License-MPL_2.0-blue.svg[License: MPL-2.0,link="https://opensource.org/licenses/MPL-2.0"]
 image:https://img.shields.io/badge/Philosophy-Palimpsest-indigo.svg[Palimpsest,link="https://github.com/hyperpolymath/palimpsest-license"]
 
 
@@ -158,7 +162,9 @@ sanctify export --guix ./project/ | aegis apply
 
 == License
 
-PMPL-1.0-or-later
+This project is licensed under the Mozilla Public License, v. 2.0. See the `LICENSE` file for details.
+
+SPDX-License-Identifier: MPL-2.0
 
 == Related Projects