"input" event should fire synchronously when input field value changes

syn fires the "input" event asynchronously when typing into a field using `syn.type(...)`. According to [the spec](https://w3c.github.io/uievents/#event-type-input) and [MDN](https://developer.mozilla.org/en-US/docs/Web/Events/input) this event should be fired synchronously as soon as the `value` property of the input has been updated.

Start by tracing how syn.type(...) handles typing into an input field and where it dispatches the "input" event. Compare the dispatch timing with the UI Events specification and verify that the event fires immediately after the value changes, using the existing relevant tests if present.

Written by the indexing model from the issue text.