[export bids] Adds basic NIRS support

[Edouard2laire]

Adds initial support for NIRS (Near-Infrared Spectroscopy) data processing within the BIDS export functionality.

This includes:

• Recognizing NIRS data based on channel types.
• Extracting NIRS-specific metadata (optode counts).
• Creating 'nirs' subfolder and using '_nirs' suffix.
• Exporting data to the SNIRF format.
• Generating an optodes coordinate file.
• Creating an events TSV file.

Note: I rebased the change from https://github.com/brainstorm-tools/brainstorm3/pull/812 to this branch so i can continue working on it while @JBusgang is busy with classes.