src/vs/editor/common/services/languageService.ts/LanguageService/createByMimeType
class LanguageService:	public createByMimeType(mimeType: string | null | undefined): ILanguageSelection {
		return new LanguageSelection(this.onDidChange, () => {
			const languageId = this.getLanguageIdByMimeType(mimeType);
			return this._createAndGetLanguageIdentifier(languageId);
		});
	}