Windows docker instructions

[jordandekraker]

It took me a long time to find the right way to mount a directory from Windows, but in the end it should have a form something like this:

docker run -it --rm -v c:\Users\jordan\Downloads\ds002168:/bids:ro -v c:\Users\jordan\Downloads\ds002168_hippunfold:/output khanlab/hippunfold:latest /bids /output participant --modality T1w -n

TODO docs updates for Windows:

• [x] point-and-click to download ds002168 from dropbox (no wget)
• [x] add absolute paths to example docker mounts
• [x] remove the \ continue line character from examples since windows cmd doesn't recognize it

Git terminal (run on windows) or another bash emulator could avoid these issues but may be more trouble for installation.

Other than these challenges the container appears to be working!

[jordandekraker]

Addressed in https://github.com/khanlab/hippunfold/pull/222