* fix: invoke the window open handler for _blank links

* feat: add disposition to setWindowOpenHandler details

* fix: pass postData to new-window event

* postData can be heterogeneous

* fix type of postBody

* fix type of UploadFile and UploadRawData to be discriminated unions

* exclude the empty string from additionalFeatures

* add a test

* add postBody and referrer to setWindowOpenHandler args

* appease typescript

* Update api-browser-window-spec.ts

* update snapshots