Add workflow and API documentation

[smoia]

Detailed Description

Our documentation lacks API and workflow documentation, i.e. the parts that document how phys2bids works. Adding it would make the life of new collaborators easier - helping them navigating through the code - and improve our transparency and support!

Possible Implementation

This is not an easy task for beginners. The people most familiar with the code should write this (those who wrote part of the code and tests), although all the help is welcome!
We need to think how to structure it, but as an example we could use tedana, bidscoin, fmriprep, etc. etc.

I will open a branch named doc/workflow in my fork (smoia/phys2bids). We can push documentation there, and once it's ready to be merged in the main program, someone else could review it and merge it.

[vinferrer]

So, You wants us to explain how each of the functions works?

[smoia]

Yep, more or less.
We could add (at least one) diagram to explain the workflow and write a couple of lines to explain better what each function does.
Generally, it means having another look at the docstrings and check that they are complete and make sense in order to prepare the API page (that, I guess, means just printing the numpydocs, like here and the raw code here ).

Maybe it's less of a big task than I imagine though.