Added Input Accessory View Support

[efremidze]

Added input accessory view support (#15) by adding a scrollView property to track panning. You also need to set the inputAccessoryView on the textField.

Observes the input accessory view through the willChangeFrame and didChangeFrame observer.

Demo has been updated to reflect the changes.

// keyboard input accessory view support
textField.inputAccessoryView = UIView(frame: toolbar.bounds)
keyboard.scrollView = tableView

// keyboard frame observer
keyboard.on(event: .willChangeFrame) { [unowned self] options in
    let height = UIScreen.main.bounds.height - options.endFrame.origin.y
    self.bottom.constant = max(0, height - self.toolbar.bounds.height)
    UIView.animate(withDuration: 0) {
        self.tableView.contentInset.bottom = max(self.toolbar.bounds.height, height)
        self.tableView.scrollIndicatorInsets.bottom = max(self.toolbar.bounds.height, height)
        self.view.layoutIfNeeded()
    }
}.start()

Im also considering an alternative implementation like BABFrameObservingInputAccessoryView.

[totocaster]

Couple of ideas on how to minimize boilerplate on developer's side.

[totocaster]

I think this can be assigned on in didSet of keyboard's scrollView, this keeping boilerplate a bit more lean on developer's part. Thoughts?

[efremidze]

Agreed

[totocaster]

Maybe we could include all of those recalculated values in options if possible? Another idea—pass toolbar configuration to keyboard and options will provide all the geometry pre-recalculated as CGRect?

[efremidze]

The main issue revolves around the toolbar height being included in the keyboard height. We need to figure out how to make this easier to handle.

[totocaster]

Another one, say we have new configuration method called toolbar(...) with all the parameters it needs to make keyboard configure itself for interactive dismissal. For example:

keyboard
    .toolbar(scrollView: self.tableView)
    .on(event: ...)
    .start()

Not sure about the name of the toolbar(...) method, but hopefully gets the point across.

[totocaster]

@efremidze Will you experiment with toolbar(...) idea? I'll experiment myself as-well and report back here.

[efremidze]

Yes Ill look into it tomorrow

[totocaster]

Can you PR this to different feature/... branch? I want to work on that too. Thanks!

[totocaster]

Awesome, thanks! Let's carry on on this branch and I'll merge it with master when all is neat and tidy.