🌐 [i18n-KO] Translated `add_new_model.md` to Korean (#24957)

* docs: ko: add_new_model.md

* feat: chatgpt draft

* fix: manual edits

* fix: change document title

* fix: edit with reviewers
Co-authored-by: Jungnerd <46880056+jungnerd@users.noreply.github.com>

* fix: edit with reviewers
Co-authored-by: Jungnerd <46880056+jungnerd@users.noreply.github.com>

* fix: edit with reviewers
Co-authored-by: Jungnerd <46880056+jungnerd@users.noreply.github.com>

* fix: edit with reviewers
Co-authored-by: Jungnerd <46880056+jungnerd@users.noreply.github.com>

* fix: edit with reviewers
Co-authored-by: SeongWooChoi <46990061+nuatmochoi@users.noreply.github.com>

* fix: edit with reviewers
Co-authored-by: SeongWooChoi <46990061+nuatmochoi@users.noreply.github.com>

* fix: edit with reviewers
Co-authored-by: SeongWooChoi <46990061+nuatmochoi@users.noreply.github.com>

* fix: edit with reviewers
Co-authored-by: Jungnerd <46880056+jungnerd@users.noreply.github.com>

* fix: add anchor to header

* Update docs/source/ko/add_new_model.md
Co-authored-by: 이서정 <97655267+sjlee-wise@users.noreply.github.com>

* Update docs/source/ko/add_new_model.md
Co-authored-by: 이서정 <97655267+sjlee-wise@users.noreply.github.com>

* Update docs/source/ko/add_new_model.md
Co-authored-by: 이서정 <97655267+sjlee-wise@users.noreply.github.com>

* fix: edit with reviews

* feat: edit toctree

---------
Co-authored-by: Wonhyeong Seo <wonhseo@kakao.com>
Co-authored-by: Jungnerd <46880056+jungnerd@users.noreply.github.com>
Co-authored-by: SeongWooChoi <46990061+nuatmochoi@users.noreply.github.com>
Co-authored-by: 이서정 <97655267+sjlee-wise@users.noreply.github.com>

docs/source/ko/_toctree.yml

@@ -145,8 +145,8 @@
 - sections:
     - local: in_translation
       title: (번역중) How to contribute to transformers?
-    - local: in_translation
-      title: (번역중) How to add a model to 🤗 Transformers?
+    - local: add_new_model
+      title: 🤗 Transformers에 새로운 모델을 추가하는 방법 
     - local: add_tensorflow_model
       title: 어떻게 🤗 Transformers 모델을 TensorFlow로 변환하나요?
     - local: in_translation