Add Component decorator host option docs

[adamdbradley]

Explain host option:

@Component({
  host: {
    theme: 'toggle',
    role: 'checkbox'
  }
)

[Hotell]

it would be also nice to update interface type definitions in core ;)

[Hotell]

Also only thing that works is theme should I re-open the issue ?

[adamdbradley]

Gah you're right! Yeah that should work.