Track the location of FunctionType declarations

[JohnnyMorganz]

Given the following type definition:

export type Foo = {
  --- Maps a value
  map: () -> any,
}

We can retrieve the FunctionType corresponding to the map prop.
On the FTV, the definition value is null, which makes sense given that its not the actual definition of the function.
Unfortunately, we therefore have no way to get the location of the FTV (i.e. Line 2, Col 7)

It would be useful to be able to get the location here. Would it make sense to have a "declaration" field as well? Or should definition be populated