Stack overflow in DodgeSizeModifier in "polygon_custom" Custom Modifier example

[richardloxley]

When copying the code for DodgeSizeModifier in example/lib/pages/polygon_custom.dart into my own app, I was getting Stack Overflow errors.

On investigating it seems to be the same error that was already fixed in the library's DodgeModifier described in #95

I was able to fix this in my code, by changing the equalTo implementation in my DodgeSizeModifier to:

  bool equalTo(Object other) {
    return other is DodgeSizeModifier;
  }

It may not be worth you fixing the example code, but I thought I'd raise an issue so if anyone else searches for this error they can find the solution.

Thanks for the library BTW!