extensions/markdown-language-features/src/preview/previewContentProvider.ts/MarkdownContentProvider/provideFileNotFoundContent
class MarkdownContentProvider:	public provideFileNotFoundContent(
		resource: vscode.Uri,
	): string {
		const resourcePath = uri.Utils.basename(resource);
		const body = localize('preview.notFound', '{0} cannot be found', resourcePath);
		return `<!DOCTYPE html>
			<html>
			<body class="vscode-body">
				${body}
			</body>
			</html>`;
	}