Add waitUntil option to support wait for networkidle0

[acbonnyac]

In my app, I have a story that uses play function to do network calls asynchronously. This worked before with storyshots puppeteer by providing waitUntil: 'networkidle0' to its gotoOption that is used with page.goto(...) function.

In Storycap, I don't see any options to provide that. I assume it's using page.goto internally when visiting each story's page. Could someone help take a look to see if that option can be exposed?