[i18n-KO] Translated index page to Korean
Author: wonhyeongseo
Pull request: yes

# What does this PR do?

Translated the `Getting started - index.mdx` file of the documentation to Korean. I use transformers for my side-project and wanted to contribute. As a beginner, this seemed appropriate.

Some questions:
- I can't access the pr documentation endpoint for Korean. Is there a missing step?
- I left all the other files alone after copying the English docs. Is this acceptable for future updates or should I add contents to the `_toctree.yml` only when translation is complete? Should I delete all other files for a cleaner review?
- In Korea, people use both `Transformer` and `트랜스포머` to describe the model. However, as this is more of a product of HuggingFace I opted not to translate it. May you please let me know which you would prefer?

Thank you in advance for your review. 

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Part of https://github.com/huggingface/transformers/issues/20179


## Before submitting
- [x] This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
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      Pull Request section?
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      to it if that's the case.
- [x] Did you make sure to update the documentation with your changes? Here are the
      [documentation guidelines](https://github.com/huggingface/transformers/tree/main/docs), and
      [here are tips on formatting docstrings](https://github.com/huggingface/transformers/tree/main/docs#writing-source-documentation).
- [ ] Did you write any new necessary tests?


## Who can review?
@sgugger, may you please review this PR?

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Models:

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Comments:
The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_20180). All of your documentation changes will be reflected on that endpoint.

The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_20180). All of your documentation changes will be reflected on that endpoint.

The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_20180). All of your documentation changes will be reflected on that endpoint.

Hey! 만나서 반가워요! Would love to hear more about the project you were working on and how transformers is used in Korea! 🤗 

Thanks a lot for your work! 
- The PR documentation endpoint was updating and should now be visible! The `KO` is not appearing because I think you did not add the file to the `toctree` indeed.
- You should delete all the other files! We don't keep template files and if someone wants to translate for futur updates, they will just copy the single file 😄 
-  I think you did a great job in keeping `Transformer` as it is indeed more the name of the library! When talking about actual `transformers` architecture, its up to you, and depends on what is more used/understandable! 

I will be glad to review once you have cleaned up the modified files! 👍🏻 Also cc @eunseojo just FYI 😉 

The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_20180). All of your documentation changes will be reflected on that endpoint.

Hello @ArthurZucker, 저도 만나서 반가워요! Thank you so much for your warm welcome and guidance.
Thank you for your help with this PR, @eunseojo 🤗 

- I made updates to `_toctree.yml` as you suggested and also added a language code to `.github/workflows/build_*_documentation`.
- So much simpler now! I translated the big section titles as they were mentioned in the `index.mdx` page. This raised errors from the pr docs workflow saying sections were empty,
![image](https://user-images.githubusercontent.com/29195190/201475900-79bb7272-1628-4591-9e37-3399c27607cf.png)
so I added a placeholder called `in_translation.mdx`. As a result, the left sidebar is a zebra now 🦓 🤣 .
![image](https://user-images.githubusercontent.com/29195190/201475993-23aa9a7d-4d63-43e3-a81f-2802e6cd71f2.png)
How would you solve this problem? 
- Yay, 🧨  thank you very much for your compliment hehe

P.S. 
I'm just a beginner but Korea, at least a community I learn lots from- [PseudoLab](https://pseudo-lab.com/), is extensively using huggingface. The government funds a yearly hackathon called [OSSCA](https://www.contribution.ac/), kinda like hacktoberfest but with dedicated mentors. RustPython and i18n-Kubernetes team got the Gold and Silver for this year. Our team AzureSDK got Bronze with 5 others.

My side-project goal is to enhance "google translator-ish" results: **to a more friendly, neighbourhood tone** in Korean (_grammar checking included_!) I'm still tinkering, just learning mostly how to get this to work. I have another idea for generating children's books, but for a later time perhaps. Thank you for your interest!

The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_20180). All of your documentation changes will be reflected on that endpoint.

The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_20180). All of your documentation changes will be reflected on that endpoint.

The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_20180). All of your documentation changes will be reflected on that endpoint.

The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_20180). All of your documentation changes will be reflected on that endpoint.

The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_20180). All of your documentation changes will be reflected on that endpoint.

Thanks for working on this! Excited to see a new doc in Korean!