`navigate()` falls through to window.location on no matching route.

Per previous conversations with @ericf.
If this looks like an acceptable solution, I can add tests.

/cc @pdokas @jeremyruppel
The options were only in there because you suggested it once upon a time :wink: I'd be satisfied leaving it up to an attribute only. Re: click handling code, are you suggesting it do something different than it does now? (Currently, the click handling code falls through to `window.location` if it doesn't route the click URL.