[Bug]: Read Directory: missing path normalization for portability

### What happened?

The Read Directory node doesn't apply any path normalization to it's output - as a result, you can't easily filter with a regex:


I suspect this may be why the glob and filter features don't seem to work on Windows either.

the reason I reached for the regex node in this case, was because [glob and exclude don't seem to work on Windows](https://github.com/Ironclad/rivet/issues/304) - so this issue might well be the root cause of that issue.

note that Windows [at the file system API level](https://learn.microsoft.com/en-us/dotnet/standard/io/file-path-formats) will canonicalize slashes - hence, for better consistency with Linux and Mac OS paths, using the forward slash on Windows should be no problem.

### What was the expected functionality?

Slashes in paths should be normalized to `/`

### Describe your environment

Win 11 Pro

### Relevant log output

_No response_

### Relevant screenshots

_No response_

### Code of Conduct

- [X] I agree to follow this project's Code of Conduct