Singularity documentation missing #3599
Description
The documentation for Singularity seems to be missing from the documentation (https://fmriprep.org/en/stable/faq.html#i-m-running-fmriprep-via-singularity-containers-how-can-i-troubleshoot-problems), more specifically https://fmriprep.org/en/stable/singularity.html. A similar issue was recently made for PETPrep (nipreps/petprep#228).