Add first devtool: prev/next arrows for broken swiping in Chrome

@incuna/js Please merge, ta!
That suffers the same problem. If you want to test for a certain type of object, we shouldn't be doing that by making assumptions about their methods or behaviour, whether that is specific methods or events.

If you specifically want to know it is definitely a router, you need to import the router and check the object prototype matches `MainRouter = instanceof(Router.protoype)`.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/instanceof

However, I'm not sure this is exactly what you want to do. What is the purpose of checking the router instance here? 
We don't seem to use `setView` anywhere, so it would be more appropriate to remove this and only check for functionality as you use it? e.g. check for methods before you run them?