assets: update preview.png and cache-bust the README reference (?v=2)

Author: alirezaabdollahpour

README.md

@@ -7,7 +7,7 @@ An interactive, scroll-driven **D3.js** data story about [**FineWeb**](https://h
 > **COM-480 Data Visualization · EPFL · Milestone 3**
 > Built on the Milestone-1 exploratory analysis ([`FineWeb_EDA.ipynb`](FineWeb_EDA.ipynb)).
 
-![Decanting the Web: the opening of the interactive data story](preview.png)
+![Decanting the Web: the opening of the interactive data story](preview.png?v=2)
 
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