chore: Add MIT License

[cmg8431]

Overview

README.md에 MIT 라이선스 관련 내용이 있지만, 실제 파일에는 빠져 있어서 추가드립니다 :)

PR Checklist

• [x] I read and included theses actions below

1. I have read the Contributing Guide
2. I have written documents and tests, if needed.

[changeset-bot[bot]]

⚠️ No Changeset found

Latest commit: 4a68eeb8330b69eed4957b972d49e1d9f8cd808c

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

Click here to learn what changesets are, and how to add one.

Click here if you're a maintainer who wants to add a changeset to this PR

💥 An error occurred when fetching the changed packages and changesets in this PR

``` Some errors occurred when validating the changesets config: The package or glob expression "es-hangul" specified in the `fixed` option does not match any package in the project. You may have misspelled the package name or provided an invalid glob expression. Note that glob expressions must be defined according to https://www.npmjs.com/package/micromatch. ```

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