Add darkmode logo (#544)

[docs] Add darkmode logo

Author: Breakthrough

README.md

@@ -1,8 +1,10 @@
 
-![PySceneDetect](https://raw.githubusercontent.com/Breakthrough/PySceneDetect/main/website/pages/img/pyscenedetect_logo_small.png)
-==========================================================
-Video Cut Detection and Analysis Tool
-----------------------------------------------------------
+<picture>
+  <source media="(prefers-color-scheme: dark)" srcset="https://raw.githubusercontent.com/Breakthrough/PySceneDetect/main/website/pages/img/pyscenedetect_logo_small_darkmode.png">
+  <img alt="PySceneDetect" src="https://raw.githubusercontent.com/Breakthrough/PySceneDetect/main/website/pages/img/pyscenedetect_logo_small.png">
+</picture>
+
+# Video Cut Detection and Analysis Tool
 
 [![Build Status](https://img.shields.io/github/actions/workflow/status/Breakthrough/PySceneDetect/build.yml)](https://github.com/Breakthrough/PySceneDetect/actions)
 [![PyPI Status](https://img.shields.io/pypi/status/scenedetect.svg)](https://pypi.python.org/pypi/scenedetect/)