DOC: add FAQ for existing FS results
DOC: add FAQ for existing FS results

oesteban/fmriprep,poldracklab/fmriprep,oesteban/fmriprep,poldracklab/preprocessing-workflow,poldracklab/preprocessing-workflow,poldracklab/fmriprep,poldracklab/fmriprep,oesteban/fmriprep