Add November 2026 article archive index

The validate:articles step requires an _index.md in every month folder.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AXY6pfEzpyB9Cjasa4B4S9

Author: trucule

content/articles/2026/11/_index.md

@@ -0,0 +1,4 @@
+---
+title: "Articles from November 2026"
+description: "PowerShell.org Articles published in November 2026."
+---