Getting ready for schema based bids-validator

[sappelhoff]

Currently there are two BIDS validator "builds":

1. the "legacy" validator, implemented mainly with custom Java Script
2. the "schema" validator, based on the BIDS schema

We use the legacy validator, but the schema validator will sooner (!) or later replace the legacy validator.

The schema validator will also be more accurate in covering the BIDS specification and might raise errors where the currently used legacy validator remained silent.

We should prepare for a switch, and the potential fixes at mne-bids that this may involve ... or at least be aware of it.

[sappelhoff]

See for example:

• ci: Include legacy validator build in deno web deployment bids-standard/bids-validator#2060

[hoechenberger]

+1 on switching sooner than later

[sappelhoff]

I think the right way would be to add an additional CI run to our suite that uses the schema validator, and then to try and make these tests pass bit by bit.

See also: https://github.com/bids-standard/bids-examples/blob/7c18d6840982518a0251cfeb59fe5c4610099ea1/.github/workflows/validate_datasets.yml#L69-L75