ENH: Add space-fsaverage to sphere_reg outputs

Co-authored-by: Taylor Salo <[email protected]>

Author: mgxd

nibabies/workflows/anatomical/outputs.py

@@ -779,6 +779,7 @@ def init_anat_derivatives_wf(
     ds_regs = pe.MapNode(
         DerivativesDataSink(
             base_directory=output_dir,
+            space='fsaverage',
             desc='reg',
             suffix='sphere',
             extension='.surf.gii',