Add @keyup event support for b-input

[caiofsouza]

For now, we can't attach :keyup event to the b-inputs comps, and it will be helpful, for example, when push the [Enter] key and submit a form or data from a field.

Thanks :D

[rafaberaldo]

Actually this is already possible:

<b-input @keyup.native.enter="enter"></b-input>

Just add the .native modifier to any event to capture natively on any component ;)