Update Streamlit example to use the GraphWidget

[FlorentinD]

The current streamlit example uses the render method.

Instead it could use the new render_widget API.
Streamlit itself doesnt support anywidget, but there seems to be a custom component https://github.com/mdrazak2001/streamlit-anywidget.
pip install streamlit-anywidget

discovered by @doyoungim999 in #274

[FlorentinD]

blocked by mdrazak2001/streamlit-anywidget#6