Update README.md

Author: AlexanderSchultheiss

README.md

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 # Classifying Edits to Variability in Source Code
 
+![Maven](https://github.com/VariantSync/DiffDetective/actions/workflows/maven.yml/badge.svg)
 [![Documentation](https://img.shields.io/badge/Documentation-Read-purple)][documentation]
 [![Install](https://img.shields.io/badge/Install-Instructions-blue)](INSTALL.md)
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