add kor courses

[maldron0309]

What does this PR do?

Add resource(s) | Remove resource(s) | Add info | Improve repo Add info

For resources

Description

Why is this valuable (or not)?

I've added git, Python, and Unity courses and updated our existing C language courses.

How do we know it's really free?

These are free, publicly available courses on YouTube

For book lists, is it a book? For course lists, is it a course? etc.

course

Checklist:

• [x] Read our contributing guidelines.
• [x] Search for duplicates.
• [x] Include author(s) and platform where appropriate.
• [x] Put lists in alphabetical order, correct spacing.
• [x] Add needed indications (PDF, access notes, under construction).
• [x] Used an informative name for this pull request.

Follow-up

• Check the status of GitHub Actions and resolve any reported warnings!

[github-actions[bot]]

Linter failed, fix the error(s):

  free-programming-books/courses/free-courses-ko.md
    73:1-80:53  warning  Alphabetical ordering: swap l.78 and l.77    alphabetize-lists  remark-lint
  210:1-213:93  warning  Alphabetical ordering: swap l.211 and l.210  alphabetize-lists  remark-lint

[github-actions[bot]]

Linter failed, fix the error(s):

  free-programming-books/courses/free-courses-ko.md
  73:1-80:53  warning  Alphabetical ordering: swap l.77 and l.76  alphabetize-lists  remark-lint