src/vs/workbench/api/browser/mainThreadCodeInsets.ts/EditorWebviewZone/constructor
class EditorWebviewZone:	constructor(
		readonly editor: IActiveCodeEditor,
		readonly line: number,
		readonly height: number,
		readonly webview: WebviewElement,
	) {
		this.domNode = document.createElement('div');
		this.domNode.style.zIndex = '10'; // without this, the webview is not interactive
		this.afterLineNumber = line;
		this.afterColumn = 1;
		this.heightInLines = height;

		editor.changeViewZones(accessor => this._id = accessor.addZone(this));
		webview.mountTo(this.domNode);
	}