src/vs/workbench/contrib/notebook/common/notebookOptions.ts/NotebookOptions/computeMarkdownCellEditorWidth
class NotebookOptions:	computeMarkdownCellEditorWidth(outerWidth: number): number {
		return outerWidth
			- this._layoutConfiguration.markdownCellGutter
			- this._layoutConfiguration.markdownCellLeftMargin
			- this._layoutConfiguration.cellRightMargin;
	}