Allow the user to access dirty rects, move rects

[daniel-abramov]

It would be great if the capture function also returned some additional "metadata" regarding the captured frame, such as dirty rects and moved rects (Desktop Duplication API supports this: 1 2).

This additional information may be crucial for developers who create screen capturing / streaming applictaions.

[bryal]

I don't have access to a windows environment, so I can't implement this feature myself. It would certainly be useful however, so I would gladly merge a pull request for this!