Update index.md

Author: halx99

docs/index.md

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 # yasio Documentation
 
-[![Release](https://img.shields.io/badge/release-v3.37.0-blue.svg)](https://github.com/yasio/yasio/releases)
+[![Release](https://img.shields.io/badge/release-v3.37.1-blue.svg)](https://github.com/yasio/yasio/releases)
 [![Docs Status](https://github.com/yasio/en/workflows/docs/badge.svg)](https://github.com/yasio/en/actions?query=workflow%3Adocs)
 
 *yasio is a multi-platform support c++11 library with focus on asio (asynchronous socket I/O) for any client application.*