[core] exported anonymous function should have named "default" instead of ""

[thepassle]

e.g.:

export default function() {}
export default () => {}

Currently shows up as:

{
  "declarations": [
    {
      "kind": "function",
      "name": ""
    }
  ],
  "exports": [
    {
      "kind": "js",
      "name": "default",
      "declaration": {
        "name": "",
        "module": "./my-element.js"
      }
    }
  ]
}

Expected:

{
  "declarations": [
    {
      "kind": "function",
      "name": "default"
    }
  ],
  "exports": [
    {
      "kind": "js",
      "name": "default",
      "declaration": {
        "name": "default",
        "module": "./my-element.js"
      }
    }
  ]
}