Update tutorials/index.qmd

saying where the 5-10x faster claim comes from

Co-authored-by: Copilot <[email protected]>

Author: rdhyee

tutorials/index.qmd

@@ -34,7 +34,7 @@ With iSamples Central currently unavailable, all tutorials now use **geoparquet
 
 Our tutorials showcase how **geoparquet + DuckDB-WASM** enables:
 - ✅ **Universal access**: No software installation required
-- ✅ **Fast analysis**: 5-10x faster than traditional approaches  
+- ✅ **Fast analysis**: 5-10x faster than traditional approaches (e.g., downloading full CSV datasets and analyzing them locally). [See benchmark](https://duckdb.org/2023/05/10/duckdb-wasm.html)
 - ✅ **Memory efficient**: Analyze 300MB datasets using <100MB browser memory
 - ✅ **Minimal data transfer**: Only download what you need
 - ✅ **Interactive exploration**: Real-time parameter adjustment