docs(readme): add SPDX header and/or standard badges

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: hyperpolymath

README.adoc

@@ -1,11 +1,14 @@
-image:https://img.shields.io/badge/License-PMPL--1.0-blue.svg[License: PMPL-1.0,link="https://github.com/hyperpolymath/palimpsest-license"]
 // SPDX-License-Identifier: PMPL-1.0-or-later
+// SPDX-FileCopyrightText: 2024-2026 Jonathan D.A. Jewell <j.d.a.jewell@open.ac.uk>
+
 = hyperpolymath.github.io
 
 :toc:
 :sectnums:
 
-// Badges
+image:https://img.shields.io/badge/OpenSSF-Best_Practices-green?logo=opensourcesecurity[OpenSSF Best Practices,link="https://www.bestpractices.dev/en/projects/new?repo_url=https://github.com/hyperpolymath/hyperpolymath.github.io"]
+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://api.thegreenwebfoundation.org/greencheckimage/github.com[Green Web,link="https://www.thegreenwebfoundation.org/green-web-check/?url=github.com"]
 image:https://img.shields.io/badge/RSR-Infrastructure-cd7f32[RSR Infrastructure]
 image:https://img.shields.io/badge/Phase-Maintenance-brightgreen[Phase]