Push SPiCiCAP dataset to our gitannex server

[valosekj]

@sandrinebedard pointed me to the following open-access dataset containing T2w (0.4x0.4x0.8mm) images for 22 healthy subjects:

https://data.mendeley.com/datasets/n2k7zz2xyt/1

It would be great to upload the dataset to our git-annex server. The dataset could be used, for example, for rootlets segmentation; context: ivadomed/model-spinal-rootlets#82