Show how to use the npm package

[rgl]

The current examples are not using the whip-whep npm package and I think they should.

For example, this is how I've used it:

npm install --save whip-whep

And from a node application:

// NB please notice that this import is different than what is in the README.md file.
import { WHEPClient } from 'whip-whep/whep'; 

const whep = new WHEPClient();
...

[jasan-s]

a working demo would be helpful