add logo

Signed-off-by: liliu-z <li.liu@zilliz.com>

Author: liliu-z

README.md

@@ -1,3 +1,7 @@
+<p>
+    <img src="static/knowhere-logo.png" alt="Knowhere Logo"/>
+</p>
+
 This document will help you to build the Knowhere repository from source code and to run unit tests. Please [file an issue](https://github.com/milvus-io/knowhere/issues/new) if there's a problem.
 
 ## Introduction