Docs: Readme (#551)

Changed the old link to a license that didn't work

Author: Radovenchyk

README.md

@@ -9,7 +9,7 @@
   <a href="https://nixos.org/">
     <img src="https://img.shields.io/static/v1?logo=nixos&logoColor=white&label=&message=Built%20with%20Nix&color=41439a&style=for-the-badge" alt="Built with nix" />
   </a>
-  <a href="https://github.com/nix-community/ethereum.nix/blob/main/LICENSE">
+  <a href="https://github.com/nix-community/ethereum.nix/blob/main/LICENSE.md">
     <img src="https://img.shields.io/badge/license-MIT%20v3.0-brightgreen.svg?style=for-the-badge" alt="License" />
   </a>
 </p>