enhancement - zero Based Counter {{forloop.counter}} -> {{forloop.zeroBasedCounter}}

[wwe-johndpope]

seems like there's some headache implementing this. Perhaps we can simply create a new method to extend this functionality?

https://github.com/ainame/Swiftkiq/blob/2bc89abc7befa87de585ffbac4d29e428919ef86/Templates/Router.stencil

[kylef]

Added in 7b9817e