Update participants guideline to newest Neurobagel schema

Update content

This issue suggests an update to an existing page in the handbook, either to correct or clarify something that is already described in the handbook. You should fill in at least the Content summary. You can leave the other sections empty if you do not know what to fill in. All sections should be filled in before starting work on the issue. Please also see our contributing guidelines for instructions on how to use this template or create another type of issue.

Content place

https://handbook.anc.plus.ac.at/data-formatting-guides/demographic_data.html

Update summary

The guide should be updated to the new Neurobagel schema, similarly to the updates in Add columns to the participant.tsv and particip... (austrian-neurocloud/metatemplates/bids-basic#9)

I propose to somehow explicitly add:

• Using the Neurobagel annotation tool is recommended.
• For additional columns, not harmonized by Neurobagel, stick to the Neurobagel output schema.

Checklist

Please indicate whether you were able to complete the sections to make it easier for the issue to be picked up.

• Content place
• Update summary