Support for const keyword in jsonshema

[gk12277]

Jsonschema supports a keyword const

type: object
properties:
  foo:
    config:
      eid: 1
    type: object
    properties:
      bar:
        cont: "ABCD"

But when generating with this there is no change in the generated file.

[koxudaxi]

@gk12277
I'm sorry for my too-late reply.
The latest version supports const.
#989