Initial marketplace: n8n-skills + doc-converter plugins

Marketplace with 2 plugins:
- n8n-skills v1.0.0 (7 skills for n8n workflow automation)
- doc-converter v1.0.0 (DOCX/PDF to HTML via Gemini Vision)

.claude-plugin/marketplace.json

@@ -0,0 +1,18 @@
+{
+  "name": "ki-brain-plugins",
+  "description": "Claude Code plugins by ki-brain: n8n workflow automation and document conversion",
+  "plugins": [
+    {
+      "name": "n8n-skills",
+      "source": "n8n-skills",
+      "description": "Complete n8n workflow automation skills (7 skills: Code JS/Python, Expressions, Patterns, Validation, Config, MCP Tools)",
+      "version": "1.0.0"
+    },
+    {
+      "name": "doc-converter",
+      "source": "doc-converter",
+      "description": "Expert guidance for DOCX/PDF to HTML conversion via Gemini Vision API",
+      "version": "1.0.0"
+    }
+  ]
+}