Implements language detection for readme.txt files to ensure compliance with WordPress.org requirement that readmes be written in standard English.

Implementation

Uses patrickschur/language-detection library to detect language with enhanced preprocessing:

Enhanced Detection Features

• ✅ Strips HTML tags, code snippets, URLs, and emails before detection
• ✅ Minimum content length (30 chars) to avoid false positives on short text
• ✅ Confidence thresholds for more accurate results
• ✅ Handles technical content without false positives

Check Locations & Severity

• Short Description and Full Description: ERROR (severity 7) - must be English

Testing

Added comprehensive test coverage:

• Fixed existing test case to properly check errors vs warnings
• Added test for English content (positive case)
• Added test for edge cases (code, URLs, technical terms)
• Created dedicated Language_Utils trait tests with 14 test cases
• Created test plugin for edge case validation

All tests pass linting and PHPStan checks.

Example Output

For non-English content:

ERROR: The readme description contains unofficial language. It must be written in standard English.

Edge Cases Handled

✅ Code snippets and technical documentation
✅ URLs and email addresses
✅ Short descriptions (< 30 chars get benefit of doubt)
✅ HTML formatting
✅ Mixed technical/natural language content
✅ Common WordPress/plugin terminology

Fixes #1009