Implement `session.new` command

[mathiasbynens]

https://w3c.github.io/webdriver-bidi/#command-session-new

[mathiasbynens]

This is blocking #110: the Firefox implementation strictly follows the spec, and requires a session to be created before accepting any non-static commands.

[mathiasbynens]

Also likely blocking #121.

[sadym-chromium]

As the session should be implemented by the embedder, our NodeJS server simply accepts all the session commands: https://github.com/GoogleChromeLabs/chromium-bidi/blob/ca2e4ba66e94b5250f86c544ecfe3e5911aab6f4/src/bidiServerRunner.ts#L48

[OrKoN]

We need this for Puppeteer. Firefox impl supports it and it's part of the spec.

[sadym-chromium]

The best the mapper can do is to send a error "500 | session not created", as the session is already exists at the point mapper is created. And the transport implementation (bidiServerRunner) should implement the proper request handling.

[sadym-chromium]

Closing, as session handling cannot be handled by the Mapper.

[OrKoN]

Re-opening this based on the latest understanding that mapper should support multiple sessions and that it should provide handling for capabilities implementable via CDP such as ignoreHTTPSErrors. This capability requires calling Security.setIgnoreCertificateErrors on every target as there is no other way to implement it in Chrome.

[OrKoN]

This has been implemented now.