Add documentation link badge to README

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

Author: mesonepigreco

README.md

@@ -1,4 +1,6 @@
 
+[![Documentation](https://img.shields.io/badge/docs-sscha.github.io%2Ftdscha-blue)](https://sscha.github.io/tdscha/)
+
 # Introduction
 
 ## What is TD-SCHA?