MRG: Restructure fNIRS IO tutorial (#9408)
MRG: Restructure fNIRS IO tutorial (#9408)

* Restructure fNIRS IO tutorial

* Apply suggestions from code review

Co-authored-by: Eric Larson <14e6e0d1a6421c3f4a71ec06bfae870e115e40b0@gmail.com>

* Update 30_reading_fnirs_data.py

* Update 30_reading_fnirs_data.py

Co-authored-by: Eric Larson <14e6e0d1a6421c3f4a71ec06bfae870e115e40b0@gmail.com>
Teekuningas/mne-python,wmvanvliet/mne-python,mne-tools/mne-python,wmvanvliet/mne-python,bloyl/mne-python,drammock/mne-python,kingjr/mne-python,kingjr/mne-python,Eric89GXL/mne-python,pravsripad/mne-python,olafhauk/mne-python,rkmaddox/mne-python,Teekuningas/mne-python,bloyl/mne-python,mne-tools/mne-python,Eric89GXL/mne-python,pravsripad/mne-python,larsoner/mne-python,kingjr/mne-python,wmvanvliet/mne-python,mne-tools/mne-python,Teekuningas/mne-python,rkmaddox/mne-python,pravsripad/mne-python,drammock/mne-python,larsoner/mne-python,olafhauk/mne-python,larsoner/mne-python,drammock/mne-python,olafhauk/mne-python