docs: add stars badge back in flat-square style

Author: GeiserX

README.md

@@ -11,6 +11,7 @@
   <a href="https://github.com/GeiserX/Wayback-Archive/releases"><img src="https://img.shields.io/github/v/release/GeiserX/Wayback-Archive?style=flat-square" alt="Release"></a>
   <a href="https://github.com/GeiserX/Wayback-Archive/blob/main/LICENSE"><img src="https://img.shields.io/github/license/GeiserX/Wayback-Archive?style=flat-square" alt="License"></a>
   <img src="https://img.shields.io/badge/python-3.8%2B-blue?style=flat-square&logo=python&logoColor=white" alt="Python 3.8+">
+  <a href="https://github.com/GeiserX/Wayback-Archive/stargazers"><img src="https://img.shields.io/github/stars/GeiserX/Wayback-Archive?style=flat-square" alt="GitHub Stars"></a>
 </p>
 
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