[Docs] Webserver docs improvement

[bramjoosten]

scope: test-webserver-js.md

Hi, just checking in. I spent a bit of time understanding how the web server option works, and I want to suggest adding the following to the intro:

A webserver does not host any files and does not have an entrypoint,but it can start up a project that lives in your codebase (for example an express.js script that loads the code you want to test).

This was not apparent from the docs and perhaps can help future devs.

[bramjoosten]

Or perhaps a variation of this which would clarify the fact that there's no entrypoint and I would still be responsible for serving the webserver itself. Perhaps "webserver" as an option name is a bit misleading too.. Not sure.

[pavelfeldman]

Please feel free to send a PR with corrections and/or clarifications for others to benefit from it! Thanks!