Change image source to github url

Author: jnnr

README.md

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 Gregor is a tool that makes your life easier when aggregating and dis-aggregating spatial data. It has been developed in the context of preparing data for energy system modeling, but can be applied in any situation involving spatial data.
 
-<img src="docs/img/polygons-to-raster-and-back.png?raw=true" width=850>
+<img src="https://raw.githubusercontent.com/jnnr/gregor/refs/heads/main/docs/img/polygons-to-raster-and-back.png" width=850>
 
 ## Installation