add check to not convert actual urls

[brendarearden]

Motivation and Context

stoplightio/prism#2385

Description

Urls were getting their their slashed converted on windows, so we need to only url.toFileSystemPath on non browser urls.

How Has This Been Tested?

Locally on mac
Locally on Windows - I do still get an error, but it is the same error that already exists https://github.com/stoplightio/json-schema-ref-parser/actions/runs/6015113363/job/16316297504

Screenshot(s)/recordings(s)

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• This PR's code follows as closely as possible the coding style/guidelines of this project.
• I have added error reporting and followed the error reporting guidelines.
• I have added event tracking and followed the event tracking guidelines.
• I have updated any relevant documentation accordingly to reflect this PR's changes.
• I have added automated tests (unit/integration/e2e/other) to cover my changes.
• All new and existing tests pass locally (excluding flaky CI tests).

[EdVinyard]

It looks good to me. I left one question (that you may have already answered and I've forgotten) and one take-it-or-leave-it suggestion.