docs: add Spark listing badge to README

Author: kadykov

README.md

@@ -11,6 +11,7 @@
 [![codecov](https://codecov.io/gh/kadykov/mcp-openapi-schema-explorer/graph/badge.svg?token=LFDOMJ6W4W)](https://codecov.io/gh/kadykov/mcp-openapi-schema-explorer)
 [![Verified on MseeP](https://mseep.ai/badge.svg)](https://mseep.ai/app/819a3ba3-ad54-4657-9241-648497e57d7b)
 [![Trust Score](https://archestra.ai/mcp-catalog/api/badge/quality/kadykov/mcp-openapi-schema-explorer)](https://archestra.ai/mcp-catalog/kadykov__mcp-openapi-schema-explorer)
+[![Listed on Spark](https://spark.entire.vc/badges/listed.svg)](https://spark.entire.vc/assets/vb-openapi-schema-explorer?utm_source=github&utm_medium=readme)
 
 An MCP (Model Context Protocol) server that provides token-efficient access to OpenAPI (v3.0) and Swagger (v2.0) specifications via **MCP Resource Templates**.