feat: add plugin manifest for Claude Code marketplace

Author: DaleSeo

.claude-plugin/plugin.json

@@ -0,0 +1,8 @@
+{
+  "name": "korean-skills",
+  "description": "Korean language skills: grammar checker, AI text humanizer, style guide enforcer",
+  "version": "1.0.0",
+  "author": {
+    "name": "DaleSeo"
+  }
+}