Add --exclude option to check-conflicts command

[TomasVotruba]

Summary

Adds an --exclude option to the check-conflicts command, so given paths can be skipped when scanning for unresolved git conflicts.

vendor/bin/swiss-knife check-conflicts . --exclude vendor --exclude tests/fixtures

Changes

• CheckConflictsCommand::run() now accepts an array $exclude = [] parameter (--exclude), passed through to the finder.
• FilesFinder::find() gained an optional array $excludedPaths = [] argument. Excluded paths are filtered out via a Finder::filter() closure (matching by str_contains on the real path, plus fnmatch for * globs), mirroring the existing PhpFilesFinder behavior since notPath() does not work with absolute paths.
• Added FilesFinderTest covering the default find, exclude-by-path, and exclude-by-glob cases.
• Documented the new option in the README.

Testing

• vendor/bin/phpunit tests/Finder/FilesFinderTest.php — passes (3 tests)
• ECS, Rector (dry-run), PHPStan (level 8) — all green
• Manual smoke test confirms a conflict in an excluded directory is skipped

Note: one pre-existing unrelated test failure in NamespaceToPSR4CommandTest exists on main and is untouched by this change.