Create Corridor security scan skill (#1)

* Create Corridor security scan skill

Add Corridor security scan skill with detailed usage instructions and guardrail knowledge.

* Rename skills/corridor/SKILL.md to plugins/corridor/skills/corridor/SKILL.md

* Update plugin.json

Author: ashwin-corridor

plugins/corridor/.cursor-plugin/plugin.json

@@ -10,5 +10,6 @@
   "repository": "https://github.com/CorridorSecurity/corridor-cursor-plugin",
   "license": "",
   "keywords": ["security", "compliance", "scanning", "mcp", "hooks", "code-review"],
-  "logo": "assets/logo.svg"
-}
+  "logo": "assets/logo.svg",
+  "skills": "./skills/"
+}