docs: document SEO and localization optimizations in v3.6.3 changelog

Author: ThisIs-Developer

CHANGELOG.md

@@ -7,7 +7,7 @@ Non-code commits (documentation, planning, README-only updates) are excluded.
 
 ## v3.6.3
 
-- **Description:** Updated application version to 3.6.3 and rotated cache namespace. Adjusted the font sizes of import, export, and language selector options in the header dropdowns to match the stats-container. Unified the language selector formatting across web and mobile layouts by displaying full language names on all devices instead of country flags on mobile.
+- **Description:** Implemented global and Asia-focused SEO & localization optimizations. Integrated a client-side multi-language translation engine in `script.js` supporting English, Simplified Chinese (简体中文), Japanese (日本語), and Korean (한국어) with automatic language detection based on browser preference (`navigator.language`) and URL parameters (`?lang=`). Localized all UI text labels, stats counters ("Min Read", "Words", "Chars"), tooltips, dialogs, and placeholders. Embedded `hreflang` alternate links and schema.org JSON-LD structured data in `index.html` to optimize search engine indexing and rich snippets. Registered search verification keys for Baidu and Naver, and added custom crawl directives in `robots.txt` and `sitemap.xml`. Scoped minor styling adjustments to align the font sizes of import, export, and language selector options in the header dropdowns with the stats-container font. Unified the language selector formatting across web and mobile layouts by displaying full language names on all devices instead of country flags on mobile. Updated application version to 3.6.3, rotated the service worker cache namespace to `markdown-viewer-cache-v3.6.3` to trigger background cache updates, and recompiled desktop app resources using `prepare.js` for offline synchronization.
 - **Date:** 2026-05-27
 - **URL:** https://github.com/ThisIs-Developer/Markdown-Viewer/commit/v3.6.3