Add CI status badge to README

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: alanhc

README.md

@@ -1,6 +1,7 @@
 Algorithm
 ========
 
+[![CI](https://github.com/alanhc/algorithm/actions/workflows/ci.yml/badge.svg)](https://github.com/alanhc/algorithm/actions/workflows/ci.yml)
 
 ## Old
 | topic | readme | links |