feat(i18n): Establish Japanese translation guidelines and update overview docs

[miyaichi]

This PR establishes standardized guidelines and a glossary for Japanese translations of the UID2 documentation. It also updates the main overview documents to align with these new standards, resolving inconsistencies in terminology and tone.

Key Changes

1. Translation Guidelines & Glossary

   • Created
     i18n/ja/TRANSLATION_GUIDELINES.md: Defines rules for style, tone, and formatting (e.g., using "desu/masu" style, keeping headers in English, using relative links).
   • Created
     i18n/ja/TRANSLATION_GLOSSARY.md: Defines standard translations for technical terms (e.g., handling of "Bid Request" vs "Bid Response", "Integration", etc.).

2. Document Updates (Japanese Version)

   • Updated i18n/ja/intro.md and i18n/ja/summary-doc-v2.md to follow the new guidelines.
   • Translated/Updated all files in overviews/ directory:
     • overview-advertisers.md
     • overview-data-providers.md
     • overview-dsps.md
     • overview-publishers.md
     • participants-overview.md
     • overview-operators-private.mdx

Standardization Details

• Bid Request/Response: Unified to Katakana terms "ビッドリクエスト" and "ビッドレスポンス".
• Integration: Primarily translated as "インテグレーション" or "実装" depending on context, avoiding "統合".
• Headers: Kept headers in English to maintain consistency with the original docs and facilitate cross-referencing.
• High-level: Omitted or translated as "概要" to avoid unnatural phrasing in Japanese.

Motivation

Previous Japanese translations lacked consistency in terminology and style. These guidelines aim to improve the quality and readability of the documentation for Japanese users while making future translation work more efficient.

[genwhittTTD]

Looks great. Thank you so much.