Updated documentation badge

Author: TheMostDiligent

template/index.html

@@ -63,7 +63,7 @@ <h1>Diligent Engine</h1>
                     <img src="https://img.shields.io/badge/License-Apache%202.0-blue.svg" alt="License">
                 </a>
                 <a href="https://diligentgraphics.github.io/docs" target="_blank">
-                    <img src="https://img.shields.io/badge/Documentation-blue" alt="Documentation">
+                    <img src="https://img.shields.io/badge/Documentation-online-0072B1?logo=readthedocs&logoColor=white" alt="Documentation">
                 </a>
             </div>
         </section>