Implementing YAML as alternative format for Schema source

[trochumski]

while composing JSON Schema using JSON seems a good idea
I find that in long run (with big schemas) it become less readable

YAML has been created to be human friendly - seem a good alternative

[lovasoa]

just the yaml parser is 30% the size of this entire package...

Maybe you could implement this by making the schema parser pluggable instead ? Then just show yaml as an example in the docs. This would be a smaller PR, just letting the user pass schemaToSource, sourceToSchema and the syntax coloring to use in monaco