Streamlit ECharts demo on Streamlit Sharing

• Install Streamlit 0.69+ and streamlit-echarts.
• Add the example source code in the corresponding module in demo_echarts or demo_pyecharts.
• Add a line for your demo in ST_xxx_DEMOS at the end of the module.
• Check that your demo has been added with streamlit run app.py.
• Request a PR.