Update README_ru.md

Author: Fenny

.github/README_ru.md

@@ -1,6 +1,11 @@
 <p align="center">
   <a href="https://gofiber.io">
-    <img alt="Fiber" height="125" src="https://raw.githubusercontent.com/gofiber/docs/master/static/img/logo.svg">
+  
+  <picture>
+    <source height="125" media="(prefers-color-scheme: dark)" srcset="https://raw.githubusercontent.com/gofiber/docs/master/static/img/logo-dark.svg">
+    <img height="125" alt="Fiber" src="https://raw.githubusercontent.com/gofiber/docs/master/static/img/logo.svg">
+  </picture>
+  
   </a>
   <br>
   <!-- base64 flags are available at https://www.phoca.cz/cssflags/ -->