fix: Ensure the keepArray node parameter is taken into the account.

[WojciechMatuszewskiStedi]

Description

First of all, thank you for this library. It's very helpful!

When I was playing with the expression to AST conversion back and forth, I noticed that the keepArray properties on a given node are not considered during the conversion from AST to a string expression.

Reproduction

Given the expression

foo.{bar: "baz"}[]

The produced AST using jsonata v1.7 yields:

{
  "type": "path",
  "steps": [
    { "value": "foo", "type": "name", "position": 3 },
    {
      "type": "unary",
      "value": "{",
      "position": 5,
      "lhs": [
        [
          { "type": "path", "steps": [{ "value": "bar", "type": "name", "position": 8 }] },
          { "value": "baz", "type": "string", "position": 15 }
        ]
      ],
      "keepArray": true
    }
  ],
  "keepSingletonArray": true
}

Now, if we serialize the above AST back to an expression form, the result is as follows:

foo.{bar: "baz"}

As you can see, we are missing the [] at the end of the expression

Uncertainty

I'm not sure what keepSingletonArray is responsible for. I would be grateful for any guidance regarding this property - mainly is my contribution correct in relation to the keepSingletonArray property as well?

[WojciechMatuszewskiStedi]

cc @loganvolkers , @00salmon