Add function type parameters

[nzakas]

For code like this:

function a<X>(b:string):X {}

The <X> is missing from the output AST. This should be represented in the typeParameters property of the FunctionDeclaration, like this:

      "typeParameters": {
        "type": "TypeParameterDeclaration",
        "loc": {
          "start": {
            "line": 1,
            "column": 10
          },
          "end": {
            "line": 1,
            "column": 13
          }
        },
        "range": [
          10,
          13
        ],
        "params": [
          {
            "type": "TypeParameter",
            "loc": {
              "start": {
                "line": 1,
                "column": 11
              },
              "end": {
                "line": 1,
                "column": 12
              }
            },
            "range": [
              11,
              12
            ],
            "name": "X",
            "bound": null,
            "variance": null,
            "default": null
          }
        ]
      }

[JamesHenry]

I'm gonna take a look at this now

[JamesHenry]

PR is in, I included an arrow function example too:

<X>(b: X): X => {
    return b;
}