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

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

Author: hyperpolymath

README.adoc

@@ -1,4 +1,6 @@
+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/SMTLib.jl"]
 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"]
 // SPDX-License-Identifier: PMPL-1.0-or-later
 = SMTLib.jl