docs(readme): add localized readmes and language links

[esphynox]

Summary

• add localized README files for the app-supported languages: Spanish, French, German, Japanese, Ukrainian, and Simplified Chinese
• add language links under the badges in the root README
• move localized README files into the Docs directory and update their internal asset and doc links

Tests

• tuist generate
• xcodebuild test -project Keyty.xcodeproj -scheme Keyty -destination 'platform=macOS'
• Other: not run; documentation-only changes

Run project commands from Apps/Keyty.

UI Changes

N/A

Before	After
N/A	N/A

Documentation

• Updated relevant docs
• No docs needed

Release Notes

Add localized README variants and language links to improve documentation discoverability for non-English readers.