fix: add missing 'skills' field to plugin.json for skill loading (#171)

The plugin.json files were missing the "skills" field which is required
for Claude Code to locate and load skills from each plugin directory.

Added "skills": "./" to 6 team-level plugin.json files:
- c-level-advisor
- engineering-team
- marketing-skill
- product-team
- project-management
- ra-qm-team

Co-authored-by: shawn.yang <shawn.yang@ikala.tv>

project-management/.claude-plugin/plugin.json

@@ -8,5 +8,6 @@
   },
   "homepage": "https://github.com/alirezarezvani/claude-skills/tree/main/project-management",
   "repository": "https://github.com/alirezarezvani/claude-skills",
-  "license": "MIT"
+  "license": "MIT",
+  "skills": "./"
 }