Add open-collective badge (#328)

Author: DefTruth

README.md

@@ -30,9 +30,11 @@
 <div align="center">
   <p align="center">
     <a href="#contribute">🔥🔥 PR Welcome: Add Your Kernel to LeetCUDA! Let's make it Awesome together! 🎉🎉</a>
+    <img src=https://opencollective.com/leetcuda/contributors.svg>
   </p>
 </div>
 
+
 ## 📖 News 🔥🔥
 <div id="news"></div>