[YAML] Implement JSON schema

[dragetd]

There is a schema description language for json and thus also yaml: http://json-schema.org/
Plus a public repository of community schemas: https://www.schemastore.org/

IntelliJ IDEA even automatically picks this up. If there was one for pom.yml, we would get basic autocompletion and documentation inside the IDE.

Anyone willing to give it a try for polyglot Maven pom.yml? :-)

[xenoterracide]

I'll consider it, after I see how converting from gradle goes. No promises, I'm stuck between forking gradle and migrating to maven with this. I'm tired of a lack of a modern solution.

[dragetd]

Kind of offtopic, but in case you are on the Kotlin side, this is a refreshing glimpse at not feeling like being stuck 30 years ago when it comes to build systems: https://github.com/JetBrains/amper :)

Also, I was considering offering to implement an alternative format in #253
Just no ideas if this is something that would be of interest.