This PR adds SQLite support to the cross-eloquent-search package, based on the community contribution in PR #58, updated for current Laravel/PHP versions.

Changes

Database Compatibility:

• Detects SQLite connection and uses appropriate SQL functions
• Uses LENGTH for SQLite vs CHAR_LENGTH for MySQL in relevance queries
• Adds explicit ORDER BY to UNION statements for SQLite compatibility
• Prefixes model keys with underscore for SQLite identifier compatibility

CI/Testing:

• Updates GitHub Actions workflow to test both MySQL and SQLite
• Adds database matrix with separate test runs for each database
• Conditionally skips fullText index creation for SQLite (MySQL-only feature)

Documentation:

• Updates README requirements to mention SQLite support
• Updates Laravel version requirement to 11+ (consistent with recent changes)

Testing

The CI workflow now runs a full test matrix:

• PHP 8.2, 8.3, 8.4, 8.5
• Laravel 11., 12.
• MySQL 8.0 + SQLite (in-memory)
• prefer-lowest + prefer-stable

SQLite tests run with :memory: database for speed and isolation.

Compatibility

• Maintains full backward compatibility with existing MySQL usage
• No breaking changes to the API
• All existing functionality works identically on both databases

Closes #58