docs: translated index page to korean (#20180)

docs: i18n: first draft of index page
docs: fix: first revision of index page
docs: i18n: missed section - supported frameworks
docs: fix: second revision of index page
review by @ArthurZucker

refactor: remove untranslated files from korean
docs: fix: remove untranslated references from toctree.yml
feat: enable korean docs in gh actions
docs: feat: add in_translation page as placeholder
docs: bug: testing if internal toc need alphabet chars
docs: fix: custom english anchor for non-alphanumeric headings
review by @sgugger

docs: i18n: translate comments on install methods in _config.py
docs: refactor: more concise wording for translations

.github/workflows/build_pr_documentation.yml

@@ -14,7 +14,7 @@ jobs:
       commit_sha: ${{ github.event.pull_request.head.sha }}
       pr_number: ${{ github.event.number }}
       package: transformers
-      languages: de en es it pt
+      languages: de en es it ko pt
     secrets:
       token: ${{ secrets.HF_DOC_PUSH }}
       comment_bot_token: ${{ secrets.HUGGINGFACE_PUSH }}