* chore: add WebContentsView.webContents helper
* chore: no need to handle webContents option
* chore: Create WebContentsView in C++
* chore: make WebContentsView accept web_preferences
* fix: nativeWindowOpen still passes WebContents to BrowserWindow
* chore: no more need of WebContentsViewRelay
* test: WebContentsView now takes options
* fix: avoid creating 2 constructors
* fix: remove cyclic references in BrowserWindow
* fix: prevent TopLevelWindow from garbage collection
* test: garbage collection of BrowserWindow
* chore: createIDWeakMap is used in tests