Allow to modify `gotoParameters`

[marcinmaruszewski]

This PR will introduce a new option for both scenarios or the general engineOptions parameter.

It will allow users to modify both Puppeteer and Playwright parameters on page.goto(url, parameters).

Examples

1. Modify general engine options

"engineOptions": {
  "gotoParameters": { "waitUntil": "networkidle0" },
}

2. Modify engine options for a single scenario

"scenarios": [
  {
    "label": "domcontentloaded",
    "url": "https://example.com"
    "gotoParameters": { "waitUntil": "domcontentloaded" },
  }
]

But why?

I've noticed that the default waitUntil parameter for Playwright which is the load value is not enough when BackstopJS is creating images for my website. In order to fix it I had to create a patch. I'd like to add it to the core as my piece of contribution.

This PR also fixes some small coding standards issues in the core/command/remote.js file.

[garris]

Great enhancement -- thank you!