Clarify preview image in README

Updated the README to clarify the preview image description.

Author: nicosuave

README.md

@@ -7,7 +7,7 @@ SQL-first semantic layer for consistent metrics across your data stack. Compatib
 
 [Documentation](https://sidemantic.com) | [GitHub](https://github.com/sidequery/sidemantic) | [Discord](https://discord.com/invite/7MZ4UgSVvF) | [Demo](https://sidemantic.com/demo) (50+ MB download)
 
-![Preview](preview.png)
+![Jupyter Widget Preview](preview.png)
 
 ## Should I use Sidemantic