Update readme

Author: brunovcosta

README.md

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 # abstra-json-sql
 
+> **warning**: This project is in its early stages and is not yet ready for production use. The API may change, and there may be bugs. Use at your own risk.
+
 `abstra-json-sql` is a Python library that allows you to **run SQL queries on JSON data**. It is designed to be simple and easy to use, while providing powerful features for querying and manipulating JSON data.
 
 ## Installation