added option to symlink (ln -s)

[cs-mshah]

This solves #31. The advantage of having symlinks (ln -s) is that we can just reference the dataset stored at some other place and create a folder structure at any/multiple desired locations as required by some codebases. Deleting symlinks doesn't delete the original dataset.

The changes have been made to support backward compatibility of move=True and move=False along with the addition of move='symlink'. All tests have successfully passed.

[a1302z]

This works wonderfully. Instead of cloning the entire dataset now, I just have links to the original image, which saves so much time and memory. I am very much in favor of merging this into the package.

[catevita]

hi, this option would be amazing, will it be integrated?

[jfilter]

Merged into main — thanks @cs-mshah! The symlink feature is now available via move='symlink'. I also refactored the duplicated copy/move/symlink logic into a shared helper and cleaned up the code with ruff.