Add Source_URL column

[dnkennedy]

so that others (with appropriate access) can get to the path of the fmriprep/nibabies results directory.

When data is private/local, this may not matter much.

But, we are also using this to collect summaries of public (S3) fmriprep results.

[dnkennedy]

Actually. Keator says make sure to call it "source_url" (all lowercase).

[dnkennedy]

@yarikoptic added a blank source_url column

TODO is to actually determine what and how to add appropriate content here...