Blueprints: JSON instead of Yaml

Coud be a nice improvement to use JSON with a json schema to build blueprints instead of Yaml.
JSON schema is well implemented in modern IDE and would prevent many blueprints error while providing autocomplete.

A YAML schema is available however, the same as a JSON schema, it comes with some disadvantages as it can’t know about plugins etc.

https://github.com/bnomei/kirby3-schema