Update README.md

Author: giovannivolpe

README.md

@@ -1,3 +1,9 @@
+<p align="center">### ⚠️ TensorFlow Compatibility Notice
+
+**DeepTrack2 version 2.0++ does not support TensorFlow.**  
+If you need TensorFlow support, please install the legacy version 1.7.
+</p>
+
 <p align="center">
   <img width="350" src=https://github.com/softmatterlab/DeepTrack2/blob/develop/assets/logo.png?raw=true>
 </p>