Added utility files for localization management:
- sync.sh: Script for syncing localizations from upstream (thunderbird-l10n, firefox-l10n)
- overrides/: Directory with override files to replace Thunderbird with МосТех.Почta after sync
- README.langpack.md: Documentation for language pack creation
The overrides/ directory contains replacement strings that are applied after syncing from upstream to maintain consistent branding.
Co-Authored-By: Z-AI