Update README to include libSQL and Turso links (#2188)

Clarify repository purpose and link to related project.

Author: penberg

README.md

@@ -33,6 +33,9 @@
 
 ---
 
+> [!NOTE]
+> This repository contains libSQL, a fork of SQLite developed by Turso. For the full SQLite rewriten in Rust (also by Turso), please visit [tursodatabase/turso](https://github.com/tursodatabase/turso).
+
 ## Documentation
 
 We aim to evolve it to suit many more use cases than SQLite was originally designed for, and plan to use third-party OSS code wherever it makes sense.