Documentation: Elaborate on url and webRoot properties

This is a request for clarifying documentation. I don't understand what problem `url` and/or `webRoot` solve:

> You may want (or need) to debug your application running on a Webserver (especially if it interacts with server-side components like Webservices).

I know when my app needs a running webserver, but I don't understand how these properties relate. I _hoped_ they fired up a web server and served my local frontend files through it. That use case comes up for me all the time, and it's time consuming to have to figure out which web server is the easiest to set up just so I can troubleshoot some HTML/JS's behavior when it's opened locally vs through a server.

I can't tell if that's what this feature does or not. To me, that quote could be interpreted either way. Can the readme include more details about what these properties do and when you need them?

Read the README section describing the url and webRoot properties, then verify from the existing documentation what each property affects and whether it starts a web server. Update the README to explain their purpose, when they are needed, and whether serving local frontend files is supported.

Written by the indexing model from the issue text.