How to add a new translation?

Assume that we are adding a new translation for new.

1. copy app/locales/en.ts to app/locales/new.ts;
2. edit new.ts, change const en: LocaleType = to const new: PartialLocaleType, and export default new;;
3. edit app/locales/index.ts:
4. import new from './new.ts';
5. add new to ALL_LANGS;
6. add new: "new lang" to ALL_LANG_OPTIONS;
7. translate the strings in new.ts;
8. submit a pull request, and the author will merge it.