Add visualizations of surface coregistration (to fsaverage)

[chrisgorgo]

https://twitter.com/michaelwaskom/status/963497405726580736

[oesteban]

Seems like the tweet that originated this is down. However, I found this other visualization

here

[mgxd]

+1 to adding some surface visualization to the reports, especially after nipreps/fmriprep#2145

[effigies]

Should consider whether to use flattened surfaces or multiple angles for surface-based visualization.

For BOLD, I would think showing the boldref resampled to the surface right after the BOLD-T1w registration (with surface contours) might make it easier to see whether the alignment makes sense. e.g., if I see a lot of dark around the temporal pole, I can look up and see drop out in the volume.