fix: use absolute URLs for language links in README (#49)

Relative paths like `docs/i18n/es/README.md` break on crates.io
because its renderer cannot resolve repo-relative paths. Use absolute
GitHub URLs so the links work both on GitHub and crates.io.

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: montfort

README.md

@@ -15,7 +15,7 @@
 [Documentation](#documentation) •
 [Contributing](#contributing)
 
-**Languages**: English | [Español](docs/i18n/es/README.md) | [简体中文](docs/i18n/zh-CN/README.md)
+**Languages**: English | [Español](https://github.com/StrangeDaysTech/devtrail/blob/main/docs/i18n/es/README.md) | [简体中文](https://github.com/StrangeDaysTech/devtrail/blob/main/docs/i18n/zh-CN/README.md)
 
 </div>