Pass previous subject through .screenshot() in new screenshot usage

[jennifer-shehane]

The new implementation of .screenshot() from #1504 documents .screenshot() always yielding null.

In the new use case of cy.get('table').screenshot(), I would like the .screenshot() to yield the previous DOM subject, the table.

This would technically be a breaking change - if someone were not following the recommendations within the docs about chaining, but honestly, I couldn't even come up with an example that would work -> then break after these updates.

[chrisbreiding]

After some discussion, we decided to yield the following object:

{
  el, // previous subject if cy.get().screenshot(), else undefined for cy.screenshot()
  path, // path to screenshot
  size, // size of screenshot (bytes)
  dimensions, // { width, height } of screenshot
  takenAt, // ISO8601 date string
  duration, // duration in milliseconds of how long it took
  pixelRatio, // pixel ratio of screenshot (determined by comparing screenshot dimensions w/ viewport dimensions)
  multipart, // boolean as to whether scrolling & stitching was necessary
  ...screenshotConfig, // all the config properties, merged from defaults, user defaults, and overrides passed to cy.screenshot()
}

[brian-mann]

screenshotConfig should just be options since they are the resolved/merged in values including what's been overridden or passed as options to cy.screenshot

[chrisbreiding]

The idea was to have it be a flat object with each option key, hence the .... I just didn't want to list every key in the screenshot config.

[brian-mann]

Released in 3.0.0.