Update default.html

Author: sichkar-valentyn

docs/_layouts/default.html

@@ -28,7 +28,7 @@
     <div id="header_wrap" class="outer">
         <header class="inner">
           <a id="forkme_banner" href="https://github.com/sichkar-valentyn/Reinforcement_Learning_in_Python">View on GitHub</a>
-          <img src="/Reinforcement_Learning_in_Python/images/Valentyn_Sichkar.png" alt="Valentyn Sichkar" width="150" height="150" />
+          <img src="/Reinforcement_Learning_in_Python/images/Valentyn-Sichkar.png" alt="Valentyn Sichkar" width="150" height="150" />
 
           <img alt="" width="230" height="230" class="avatar width-full rounded-2" src="https://avatars3.githubusercontent.com/u/34546286?s=460&amp;v=4" />