src/vs/workbench/contrib/notebook/browser/view/renderers/webviewPreloads.ts/MarkupCell/constructor
class MarkupCell:		constructor(id: string, mime: string, content: string, top: number) {
			this.id = id;
			this.mime = mime;
			this._content = content;

			let resolveReady: () => void;
			this.ready = new Promise<void>(r => resolveReady = r);

			const root = document.getElementById('container')!;

			this.element = document.createElement('div');
			this.element.id = this.id;
			this.element.classList.add('preview');
			this.element.style.position = 'absolute';
			this.element.style.top = top + 'px';
			this.toggleDragDropEnabled(currentOptions.dragAndDropEnabled);
			root.appendChild(this.element);

			this.addEventListeners();

			this.updateContentAndRender(this._content).then(() => {
				resizeObserver.observe(this.element, this.id, false);
				resolveReady();
			});
		}