* 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
