Translator에 Libretranslate 지원 추가

[JammyDodger]

이제 병합되었습니다

Ember 비추천 경고: Translator 플러그인 관련

This is now merged, sorry again for the very long delay. From a quick test, LibreTranslate seems like a great open-source alternative to paid services. (Will update the OP instructions as well.)