Explore testing links on Windows

[lread]

Babashka fs tests currently skip link tests for Windows.

Windows does not allow symbolic links by default, but they can be enabled for NTFS.

I don't know about hard links, I would have to look into that.

Explore the viability of testing bb fs link fns on Windows for dev and CI.

If it works out, I would also add a brief note to the README.

Might also allow such tests to be optionally skipped through metadata, for devs that haven't set this up on their Windows boxes.