FR: support YAML schema validation

[ramiromagno]

Example: The GWAS Catalog Summary Statistics Format (GWAS-SSF)

The metadata YAML file of the GWAS-SSF standard obeys a schema standard.

• YAML example: https://github.com/EBISPOT/gwas-summary-statistics-standard/blob/master/examples/0000123.tsv-meta.yaml
• YAML schema: https://github.com/EBISPOT/gwas-summary-statistics-standard/blob/master/schema/metadata-yamale-schema.yaml

Seemingly this validation can be achieved with https://github.com/23andMe/Yamale, a python tool.

How hard would it be to perform this in R?

[spgarbet]

It would be quite difficult with the way the library is structured. The library is built around a yaml1.1 parser library that has not made the transition to yaml1.2.