Add possibility to cancel from onShow event

[emilpalsson]

Like tippy.js does (see code & documentation), allow the onShow callback to return false to cancel showing the tooltip.

Very useful for conditionally showing the tooltip depending on e.g. if the hovered content is currently overflown or not. I use it like this:

onShow={el => {
  const isTextOverflown = el.parentNode.offsetWidth < el.parentNode.scrollWidth
  return isTextOverflown
}}

I also added el as an argument to the callback. If you think that's a bad idea, I'll happily change.

[emilpalsson]

I could also happily add the same cancellation option to onHide. Again, like tippy.js does.

[emilpalsson]

I would love to hear back from you on this super small and straight forward PR. Thanks!

[atomiks]

@emilpalsson why aren't you using the official library? https://github.com/atomiks/tippyjs-react

[emilpalsson]

@atomiks I wasn't aware there was one. Awesome, will definitely look into it! Thanks!

[emilpalsson]

@emilpalsson why aren't you using the official library? https://github.com/atomiks/tippyjs-react

@atomiks Just wanted to tell you that we've now fully migrated to the official library and our current use case (conditionally show tooltip using the onShow prop) worked out of the box. Thanks alot!