Press 'i' (information) to print context info

Introduce new hotkey bound to 'i' that prints current context info, including:

- full path of the config file
- list of URLs to watch
- list of enabled plugins
- ip and port the proxy is listening on
- troubleshooting link (https://aka.ms/devproxy/help)

When you run proxy, some of this information is not visible and some of it is scrolled beyond the terminal window boundaries. It's annoying to have to stop and start the proxy to get this information. Being able to press 'i' to have proxy print this information on demand makes it easier to see what's enabled and running in case you need this information mid-flight.

The output of this information should be sent to stderr so that it's not mixed with proxy's default output