Update webhooks docs to show what request is actually done

[doc-l]

It would be very helpful is the webhook documentation in the README actually showed what request is done with what parameters (ie: a GET or POST request with this and that querystring / body) instead of an express example. I don't use express so I now have to do trial and error to get the correct response.

Thanks!

[doc-l]

ah I now see that there is a swagger doc. Might be helpful to link from the github readme to the docs :)

[chaseeb]

was this resolved?

[doc-l]

Not really, but I'll close this and merge with #7