Support ES6-style compact object literals for multiselect

[danvk]

Say I have this JSON object and want to pare it down to just the ids and first names:

{
  "values": [
    {"id": 1, "first": "Bill", "last": "Gates"},
    {"id": 2, "first": "Larry", "last": "Page"}
  ]
}

I can do that with this expression: values[*].{id:id, first:first}.

Since {x:x, y:y} is such a common pattern, ES6 introduced compact object literal notation to simplify this. In ES6, {x,y} is equivalent to {x:x, y:y}.

I don't believe {x,y} is valid in JMESPath, so it would be a boon (and intuitive to JS users) to add this to the spec.