docs: add yml syntax highlighting to code block

Co-authored-by: neilime <314088+neilime@users.noreply.github.com>

Author: Copilot

.github/workflows/continuous-integration.yml

@@ -88,7 +88,7 @@ on:
           Accepts either a string (container image name) or a JSON object with container options.
 
           String format (simple):
-          ```
+          ```yml
           container: "node:18"
           ```