🐛 fix: set initial size and use proper window on event

[iammola]

The initial onDidDimensionsChange event is fired with { width: 0, height: 0} without the initial set size and the resize event still referenced the parent widow's sizing.

[codesandbox-ci[bot]]

This pull request is automatically built and testable in CodeSandbox.

To see build info of the built libraries, click here or the icon next to each commit SHA.

Latest deployment of this branch, based on commit 6881daa593b3f9b769c2021983cb4d85565634cd:

Sandbox	Source
customheader-dockview	Configuration
dockview-app	Configuration
editor-gridview	Configuration
events-dockview	Configuration
externaldnd-dockview	Configuration
fullwidthtab-dockview	Configuration
iframe-dockview	Configuration
keyboard-dockview	Configuration
lockedgroup-dockview	Configuration
nativeapp-dockview	Configuration
nested-dockview	Configuration
rendering-dockview	Configuration