docs: add badge

Author: zhangyu94

README.md

@@ -7,6 +7,9 @@
 <a href="http://commitizen.github.io/cz-cli/">
     <img alt="Commitizen friendly" src="https://img.shields.io/badge/commitizen-friendly-brightgreen.svg">
 </a>
+<a href="https://pepy.tech/projects/oldvis_dataset">
+    <img alt="Pepy Total Downloads" src="https://img.shields.io/pepy/dt/oldvis_dataset">
+</a>
 
 # oldvis_dataset