Handle websockets properly

[na--]

This issue was prompted by https://community.k6.io/t/k6-unsupported-protocol-scheme-wss/781. At a first pass, we probably should ignore websocket connections for now, merely adding a comment in the generated k6 script, so we don't cause errors. In the long-term, it might be possible to also convert them into k6 websocket connections, though that will probably have a ton of issues.

[mstoykov]

The second part (actually making websocket requests) should probably wait for an async websocket support in k6

[legander]

I suppose these are related. #63

[legander]

Here is a potential first remedy to at least make it clear that non http(s)? urls wont end up in the generated k6 script.

• Generate a script comment including the non http url.
• Log the non http url with a warning saying "url with protocol ... not supported, skipping." har generated from chrome produces: "Missing request method (24)" #63 (comment)