src/vs/editor/standalone/browser/standaloneCodeEditor.ts/createTextModel
export function createTextModel(modelService: IModelService, languageService: ILanguageService, value: string, languageId: string | undefined, uri: URI | undefined): ITextModel {
	value = value || '';
	if (!languageId) {
		const firstLF = value.indexOf('\n');
		let firstLine = value;
		if (firstLF !== -1) {
			firstLine = value.substring(0, firstLF);
		}
		return doCreateModel(modelService, value, languageService.createByFilepathOrFirstLine(uri || null, firstLine), uri);
	}
	return doCreateModel(modelService, value, languageService.createById(languageId), uri);
}