Add contributors section to README

Added a contributors section to acknowledge contributions.

Author: kittendevv

README.md

@@ -53,6 +53,14 @@
 
 </details>
 
+## 💖 Contributors
+
+Invio is made possible by your contributions!
+
+<a href="https://github.com/kittendevv/Invio/graphs/contributors">
+  <img src="https://contrib.rocks/image?repo=kittendevv/Invio" />
+</a>
+
 ## 🤝 Contributing
 
 - Found a bug or have an idea? Open an issue.