Add FAQ page to docs

docs/faq.rst

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+.. include:: links.rst
+
+##########################
+Frequently Asked Questions
+##########################
+
+.. contents:: Table of Contents
+   :local:
+   :depth: 1
+
+*************************************
+Should I use *XCP-D* for my analysis?
+*************************************
+
+This is a complicated question.
+*XCP-D* is designed for resting-state or pseudo-resting-state functional connectivity analyses.
+It also produces a number of resting-state-specific derivatives, including ALFF and ReHo.
+
+If your goal is just to denoise your resting-state data, *XCP-D* may be overkill.
+You can perform simple denoising with tools like Nilearn or FSL.
+
+*XCP-D* is not designed as a general-purpose postprocessing pipeline.
+It is really only appropriate for certain analyses,
+and other postprocessing/analysis tools are better suited for many types of data/analysis.
+
+*XCP-D* derivatives are not particularly useful for task-dependent functional connectivity analyses,
+such as psychophysiological interactions (PPIs) or beta series analyses.
+It is also not suitable for general task-based analyses, such as standard task GLMs,
+as we recommend including nuisance regressors in the GLM step,
+rather than denoising data prior to the GLM.
+
+
+***************************************************
+How do you decide what steps to include in *XCP-D*?
+***************************************************
+
+We have tried to follow current best practices in the field for processing and denoising
+resting-state data.
+While there are always new methods being developed, we have limited *XCP-D* to methods that
+have been validated and are commonly used in the field.
+If there is a method you would like to see included in *XCP-D*, please open an issue on GitHub,
+but please be aware that we may not be willing to include all methods.
+
+
+*******************************************************
+Can I use XCP-D on my data if it is not in BIDS format?
+*******************************************************
+
+No. *XCP-D* is designed to work with BIDS-formatted data.
+Since *XCP-D* uses preprocessed data (i.e., data from a BIDS Derivatives dataset) and
+the BIDS Derivatives dataset structure is not finalized, we largely follow the conventions
+of NiPreps BIDS apps (especially fMRIPrep) for the input data.

docs/index.rst

@@ -17,6 +17,7 @@ Contents
    usage
    workflows
    outputs
+   faq
    contributing
    api
    changes