Update README.md

Add another tool which helps visualize COSBench results.

Author: Yaguang Wang

README.md

@@ -70,5 +70,7 @@ COSBench-Workload-Generator: (https://github.com/giteshnandre/COSBench-Workload-
 
 COSBench-Plot: (https://github.com/icclab/cosbench-plot)
 
+matplotlib-utils-cosbench: (https://github.com/wallnerryan/matplotlib-utils-cosbench)
+
 
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