Update README.md to handle both light and dark themes

README.md

@@ -35,7 +35,7 @@ This repository contains the following directories:
 ## Usage 
 This project was created with Azure in mind and therefore the main scripts are meant for usage on Azure. 
 
-![usage_img](docs/assets/usage.png)
+<picture><source srcset="docs/assets/usage_dark.png" media="(prefers-color-scheme: dark)"/><source srcset="docs/assets/usage_light.png" media="(prefers-color-scheme: light), (prefers-color-scheme: no-preference)"/><img src="docs/assets/usage_light.png" /></picture> 
 
 ### 1. Preprocessing
 1. First step is to download the LIDC-IDRI dataset on Azure Virtual Machine. The `azure/virtual_machine/download_dataset.sh` script is meant for this task.