add stimulus software info to JSON

[Remi-Gau]

Given that I pushed to add that in the BIDS specs, it would be logical to make CPP_BIDS add this info into the JSON.

https://bids-specification.readthedocs.io/en/stable/04-modality-specific-files/05-task-events.html#stimulus-presentation-details.

This will require some synchronisation with CPP_PTB that also has a getOSinfo function:

CPP_PTB/src/initPTB.m

Line 106 in 9536de7

function cfg = getOsInfo(cfg)