Extension (probably) doesn't work on Windows (without WSL)

[Tabby]

I haven't had time to fully test and verify this, but I'm pretty sure that currently there are likely to be some path handling issues that mean that this extension (both the rewrite and the main versions I think) don't work correctly on Windows. WSL is fine, as that's Linux running in a virtualised environment on Windows.

More of a chore than anything else, I think what needs doing for this is the following:

• Add/extend tests for any path handling methods and classes to verify that they handle Windows paths correctly
• Fix any issues found (using Node's path functions as much as possible to normalise the way we handle paths)
• Manually test that everything works correctly

It might be beneficial to do some refactoring so that all path handling code is in one or more separate classes from everything else, so that there's only one place in the codebase where developers have to think about handling both types of paths, and everywhere else can just use the abstractions.