Add eyetracking support

[smoia]

Detailed Description

Eyetracking is not supported in BIDS 1.2.2 yet, but it's a proposed extension that seems to be nearly completion.
It might or might not be considered physiological data, but for sure we could start adding a workflow that would support eyetracking BIDSification into phys2bids.

Context / Motivation

At the moment and to my knowledge, there is no public program/repository that support BIDS format for eyetracking data. We could help people that collect eyetracking to share them by being between the early supporters!

Possible Implementation

• Read the Eyetracking extension proposal for BIDS
• Have a look at eyetracking data and understand its structure
• Look for python based libraries that read such data
• Write an interface function that implements those libraries (or simply reads such data)
• Tweak the main workflow to be able to read and process eyetracking files.