README: Update logo

Introduce logo for dark version of github

Author: hynekkar

README.md

@@ -1,5 +1,6 @@
 <p align="center">
-    <img src="https://raw.githubusercontent.com/CESNET/ipfixprobe/refs/heads/master/docs/images/ipfixprobe-horizontal.svg" width="450">
+    <img src="https://raw.githubusercontent.com/CESNET/ipfixprobe/refs/heads/master/docs/images/logo/logo_horizontal_color.svg" width="450">
+    <img src="https://raw.githubusercontent.com/CESNET/ipfixprobe/refs/heads/master/docs/images/logo/logo_horizontal_white.svg" width="450" media="(prefers-color-scheme: dark)">
 </p>
 
 [![](https://img.shields.io/badge/license-BSD-blue.svg)](https://github.com/CESNET/ipfixprobe/blob/master/LICENSE)