Infer field type from const value

[LucianBuzzo]

This change adds support for schemas that use the const keyword
without and adjacent type keyword. For example:

{
  "type": "object",
  "properties": {
    "firstName": {
      "const": "Chuck"
    }
  }
}

Signed-off-by: Lucian lucian.buzzo@gmail.com

Checklist

• I'm updating documentation
  • I've checked the rendering of the Markdown text I've added
• I'm adding or updating code
  • I've added and/or updated tests
  • I've updated docs if needed
  • I've run npm run cs-format on my branch to conform my code to prettier coding style
• I'm adding a new feature
  • I've updated the playground with an example use of the feature

[epicfaace]

Looks good! I think it might be good to add a test for a const equal to a boolean and make sure the checkbox widget is rendered?

[LucianBuzzo]

@epicfaace Good idea, I've added the test