[EDF to BIDS revision] Unclear explanation about how to extract `Startime` and `Stoptime` metadata

[celprov]

https://github.com/TheAxonLab/hcph-sops/blob/c370b0461b197c78716e33b602214c31e6a5acc3/docs/data-management/edf-to-bids.md?plain=1#L51-L83

• [ ] L52: Looking at a _eyetrack_physio.json, it is not clear to me what those events described in the JSON are
• [ ] L54: how are the message_first_trigger and message_last_trigger initialized (probably related to #455)
• [ ] L71, L78: why do we extract the last start message and the first stop message?