Add a "fade-in-duration" property to QTooltip component #588

Hi, :)

I just upgraded from Quasar v0.16 to v0.17.12 and a fade-in effect is now added by default to q-tooltip content. I find it slow and I think it could be great to have a property in component which permits to set it. Maybe something like that :

<div>
  ...
  <q-tooltip fade-in-duration="300">My tooltip</q-tooltip>
</div>

Thank you very much.