updated visualization command (#326)

Author: MARVEBUKA

CONTRIBUTING.md

@@ -119,7 +119,7 @@ source venv/bin/activate
 (venv) pip install ".[all]"
 # Create the HTML to visualize locally
 (venv) make html
-(venv) open _build/index.html
+(venv) open _build/html/index.html
 # Or you can start a serve that watches for local file changes
 (venv) make watch
 # Open <http://localhost:8000/> in your browser