Add a maintenance notice

The project is currently not actively maintained, this notice help to
set clear expectations for users & contributors.

Closes #790

Author: philpep

README.rst

@@ -1,3 +1,8 @@
+> [!IMPORTANT]
+> **Maintenance Notice**
+>
+> This project is currently **not actively maintained**, and responses to issues or pull requests may be delayed for **several months**. Please consider this when using the project and feel free to contribute via pull requests, which will be reviewed as time permits. Thank you for your understanding!
+
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 Testinfra test your infrastructure
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