Update notebook file name and add README.md

Author: ayman-openai

examples/vector_databases/duckdb/README.md

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+# DuckDB  
+
+[DuckDB](https://duckdb.org/) is an in-process SQL OLAP database management system designed for analytics.  
+DuckDB provides a lightweight, efficient way to query and store embeddings directly alongside your structured data, making it easy to combine vector operations with rich SQL analytics.  
+
+For technical details, refer to the [DuckDB documentation](https://duckdb.org/docs/).  
+
+The [`duckdb`](https://github.com/duckdb/duckdb) GitHub repository contains the source code, examples, and community resources for experimenting with DuckDB.