MNT: Add netbase to Docker image to ensure correct datalad operation

[effigies]

This creates the /etc/protocols file that allows Haskell (git-annex) to fetch web objects. Without it you can get responses like:

$ singularity exec code/containers/images/bids/bids-fmriprep--21.0.0.sing datalad get sourcedata/templateflow/tpl-OASIS30ANTs/tpl-OASIS30ANTs_res-01_T1w.nii.gz
get(error): sourcedata/templateflow/tpl-OASIS30ANTs/tpl-OASIS30ANTs_res-01_T1w.nii.gz (file) [https://files.osf.io/v1/resources/ue5gx/providers/osfstorage/5bc647b153cec4001aadab65 download failed: ConnectionFailure Network.BSD.getProtocolByName: does not exist (no such protocol name: tcp)
downloading from all 1 known url(s) failed
https://files.osf.io/v1/resources/ue5gx/providers/osfstorage/5bc647b153cec4001aadab65 download failed: ConnectionFailure Network.BSD.getProtocolByName: does not exist (no such protocol name: tcp)
downloading from all 1 known url(s) failed
https://files.osf.io/v1/resources/ue5gx/providers/osfstorage/5bc647b153cec4001aadab65 download failed: ConnectionFailure Network.BSD.getProtocolByName: does not exist (no such protocol name: tcp)
downloading from all 1 known url(s) failed]
action summary:
  get (error: 1, notneeded: 1)

Fix found on commercialhaskell/stack#2372 (comment).

[effigies]

Assuming this doesn't break the build, will merge, then merge forward into maint/21.0.x.