docs: translate banner to Korean

[ho8ae]

React Conf 배너 한국어 번역 추가

변경 사항

• "Join us for React Conf on Oct 7-8. Learn more." → "10월 7-8일 React Conf에 함께하세요. 더 알아보기."

번역 방향

• 자연스러운 한국어 표현 사용
• 간결하고 명확한 문구로 번역

필수 확인 사항

• 기여자 행동 강령 규약^{Code of Conduct}
• 기여 가이드라인^Contributing
• 공통 스타일 가이드^{Universal Style Guide}
• 번역을 위한 모범 사례^{Best Practices for Translation}
• 번역 용어 정리^{Translate Glossary}
• textlint 가이드^{Textlint Guide}
• 맞춤법 검사^{Spelling Check}

선택 확인 사항

• 번역 초안 작성^{Draft Translation}
• 리뷰 반영^{Resolve Reviews}

[vercel]

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1 Skipped Deployment

Name	Status	Preview	Comments	Updated (UTC)
ko-legacy-reactjs-org	⬜️ Ignored (Inspect)	Visit Preview		Aug 8, 2025 4:55am

[github-actions]

Size changes

📦 Next.js Bundle Analysis for undefined

This analysis was generated by the Next.js Bundle Analysis action. 🤖

Five Pages Changed Size

The following pages changed size from the code in this PR compared to its base branch:

Page	Size (compressed)	First Load
/404	130.53 KB (🟡 +9 B)	240.97 KB
/500	130.52 KB (🟡 +9 B)	240.97 KB
/[[...markdownPath]]	132.59 KB (🟡 +9 B)	243.03 KB
/errors	130.67 KB (🟡 +9 B)	241.11 KB
/errors/[errorCode]	130.64 KB (🟡 +9 B)	241.09 KB

Details

Only the gzipped size is provided here based on an expert tip.

First Load is the size of the global bundle plus the bundle for the individual page. If a user were to show up to your website and land on a given page, the first load size represents the amount of javascript that user would need to download. If next/link is used, subsequent page loads would only need to download that page's bundle (the number in the "Size" column), since the global bundle has already been downloaded.

Any third party scripts you have added directly to your app using the <script> tag are not accounted for in this analysis

Next to the size is how much the size has increased or decreased compared with the base branch of this PR. If this percentage has increased by 10% or more, there will be a red status indicator applied, indicating that special attention should be given to this.

[lumirlumir]

LGTM, 기여 감사드립니다!