feat[ignore]: Add path() to error

[tmccombs]

Add a path() method to Error, which allows getting the path without needing to pattern match on WithPath.

[BurntSushi]

Hmmm I'm not so sure about this one. This is omitting Error::Io and Error::Loop and Error::Partial. In the latter two cases, it's not clear what Path should be provided. I think this one might be better as a helper function defined as needed for your specific use case.