Support for powershell commands

[bmansour1]

Link to doc page in question (if any): https://github.com/streamlit/streamlit/wiki/Contributing Name of the Streamlit feature whose docs need improvement: installing for web development What you think the docs should say: I think the doc should specify to users that they must be using WSL and not powershell and also provide documentation for how to set streamlit up with powershell.