Fix typos and spacing in Korean docs

[leejh0820]

Fix typos and spacing in Korean first-contribution docs
Add Jeonghyun Lee to Contributors list

Before submitting this pull request, check the changes to see it's only the changes you made intentionally
If there are changes to other lines you didn't make deliberately, it's possible that your IDE made the changes with a utility like prettier.
Next time, make sure that you only add your changes by using git add -p and rather than git add Contributors.md

If you're doing something in the checklist below, put an x inside [ ] so that - [ ] becomes - [x]

• I had fun going through this tutorial (ノ^o^)ノ and learned on the way ٩(＾◡＾)۶
• There are some things I'd like to improve in this tutorial. I have written them below.
• There were steps where I had errors while following this tutorial. I have written them below.

[github-actions]

Thank you for your pull request. This pull request contains changes in files which requires review. The following files were changed:

• Contributors.md
• docs/translations/README.ko.md

[rammba]

Hello @leejh0820, can you maybe add yourself to the CONTRIBUTING.md. Doing that, everyone can find you and ask for help about future Korean translations.