Add minimum n8n version requirement to README (#207)

* Initial plan

* Add minimum n8n version requirement (2.7.0) to README

Co-authored-by: rbrighenti <202984599+rbrighenti@users.noreply.github.com>

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Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: rbrighenti <202984599+rbrighenti@users.noreply.github.com>

Author: Copilot

nodejs/n8n/sample-agent/README.md

@@ -9,7 +9,7 @@ This sample demonstrates how to build an agent using n8n with its Microsoft Agen
 ## Prerequisites
 
 - Microsoft Agent 365
-- n8n instance with Microsoft Agent 365 Node
+- n8n instance (version 2.7.0 or later) with Microsoft Agent 365 Node
 
 ## Running the Agent