[TECO-6] <docs>: Add snap badge.

README.md

@@ -3,6 +3,7 @@
 [![Coverage Status](https://coveralls.io/repos/github/taosdata/TDengine/badge.svg?branch=develop)](https://coveralls.io/github/taosdata/TDengine?branch=develop)
 [![CII Best Practices](https://bestpractices.coreinfrastructure.org/projects/4201/badge)](https://bestpractices.coreinfrastructure.org/projects/4201)
 [![Docker Pulls](https://img.shields.io/docker/pulls/tdengine/tdengine)](https://hub.docker.com/repository/docker/tdengine/tdengine)
+[![tdengine](https://snapcraft.io//tdengine/badge.svg)](https://snapcraft.io/tdengine)
 
 [![TDengine](TDenginelogo.png)](https://www.taosdata.com)