Update examples to demonstrate using object for levels in sidecar for TSV

[Remi-Gau]

Should implement: bids-standard/bids-specification#1603
Could then be used to test the validator.

I would recommend updating an example that has no participants.json

[Remi-Gau]

Good candidate datasets:

• should have more than one subjects
• should not have a participants.json
• should have a participant.tsv with more the the subject_id column

[Remi-Gau]

potential good candidates:

• https://github.com/bids-standard/bids-examples/blob/master/7t_trt/participants.tsv
• https://github.com/bids-standard/bids-examples/blob/master/eeg_ds000117/participants.tsv
• https://github.com/bids-standard/bids-examples/blob/master/ds000117/participants.tsv
• https://github.com/bids-standard/bids-examples/blob/master/ds008/participants.tsv
• https://github.com/bids-standard/bids-examples/blob/master/ds009/participants.tsv
• https://github.com/bids-standard/bids-examples/blob/master/ds101/participants.tsv
• https://github.com/bids-standard/bids-examples/blob/master/ds102/participants.tsv
• https://github.com/bids-standard/bids-examples/blob/master/ds108/participants.tsv
• https://github.com/bids-standard/bids-examples/blob/master/ds110/participants.tsv
• https://github.com/bids-standard/bids-examples/blob/master/ds114/participants.tsv
• https://github.com/bids-standard/bids-examples/blob/master/ds116/participants.tsv