Light logo for light mode and dark for dark (#649)

* specify for dark mode

* push image

* image for light mode

Author: arjxn-py

docs/source/assets/jupytercad-light-ss.png

@@ -6,7 +6,8 @@ JupyterCAD is a JupyterLab extension for 3D geometry modeling with collaborative
 
 JupyterCAD has support for FreeCAD files, which makes it easy to import and export models from FreeCAD. It also has a range of features for creating and manipulating 3D shapes, including a variety of primitives, transformations, and Boolean operations.
 
-![jupytercad](https://raw.githubusercontent.com/jupytercad/JupyterCAD/refs/heads/main/docs/source/assets/jupytercad-screenshot.png)
+![jupytercad](https://raw.githubusercontent.com/jupytercad/JupyterCAD/refs/heads/main/docs/source/assets/jupytercad-screenshot.png#gh-dark-mode-only)
+![jupytercad](https://raw.githubusercontent.com/jupytercad/JupyterCAD/refs/heads/main/docs/source/assets/jupytercad-light-ss.png#gh-light-mode-only)
 
 ## Requirements