add v6 discussions to 4.1 branch (#195)

Author: Arhell

mkdocs.yml

@@ -2570,4 +2570,5 @@ nav:
           - Helper: helper.md
           - Registry: registry.md
   - Discussions: https://github.com/orgs/phalcon/discussions
+  - Discussions(v6): https://github.com/phalcon/phalcon/discussions
   - Blog: https://blog.phalcon.io/