Allow passing options directly to Puppeteer's `Page.setViewport()` function

[jerboa88]

Allow options to be passed directly to Puppeteer's Page.setViewport() like so:

setDefaultOptions({
  puppeteer: {
    setViewport: {
      deviceScaleFactor: 1.5,
      isLandscape: true,
      isMobile: true,
      // ...
    },
    // ...
  },
  // ...
})

Allowing arbitrary options to be passed will give user's more flexibility in case they need to customize the behavior of Page.setViewport() for their use case.

Options important for correct behavior of the plugin like width and height should overwrite user-provided options.