Contribute Server Extensions to Streamlit

[rmorshea]

In order to more natively support IDOM in Streamlit we need to contribute the ability to register "server extensions" with Streamlit's underlying web server. At the moment this is not supported, but I've created an issue for it: streamlit/streamlit#2825

Until then, we might have to make a custom runner that waps Streamlit. Usage might then look like:

idom-streamlit my_script.py

Since this would allow us access to the web server instance before it starts running.