Add spec_url for window.closed (#11403)
Add spec_url for window.closed (#11403)

Co-authored-by: Philip Jägenstedt <3ba3974e96044dcde818e6310ed799abe10671d4@foolip.org>
mdn/browser-compat-data,mdn/browser-compat-data,chrisdavidmills/browser-compat-data,chrisdavidmills/browser-compat-data