Use yaml instead of json

[YooSunYoung]

Just an idea at the moment,

Our configurations and metadata parsing configurations are complicated and requires many steps.
We need to keep the explanation along with the configuration but json officially doesn't allow comments.
beamlime uses yaml and yaml allows comments.

If we decide to go form yaml instead of json, it should be done before other people start using it.

• Write ADR about it
• Update json part to yaml.