Add a chai plugin to check for path equality

[matthewbastien]

Description

Make it easier to check for path equality in tests by creating a new chai plugin. It can be used like so:

expect(somePath).to.equalPath("/path/to/some/file.txt");

This assertion converts both paths to the same file separator before comparison to ensure consistent behavior on all platforms.

Tasks

• Required tests have been written
• [ ] Documentation has been updated
• [ ] Added an entry to CHANGELOG.md if applicable