add Plano agent skills framework and rule set (#797)

* feat: add initial documentation for Plano Agent Skills

* feat: readme with examples

* feat: add detailed skills documentation and examples for Plano

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Co-authored-by: Adil Hafeez <adil.hafeez@gmail.com>

skills/metadata.json

@@ -0,0 +1,8 @@
+{
+  "version": "1.0.0",
+  "organization": "Plano",
+  "name": "plano-agent-skills",
+  "abstract": "Best practices for building agents and agentic applications with Plano — the AI-native proxy and dataplane. Covers configuration, routing, agent orchestration, filter chains, observability, CLI operations, and deployment patterns.",
+  "homepage": "https://github.com/katanemo/archgw",
+  "license": "Apache-2.0"
+}