Make `scrollTabsRight` less fragile

See discussion

The timeout is for the css animation. I still want to show the css animation. Got a better way to scroll? I should measure it. I made an issue for that.

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transitionEnd would be better right? Also the comment above this is a little wrong, it says 0.1 seconds but the actual timeout is 0.2 seconds.

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It seems that Vue can listen for CSS transitions?

https://vuejs.org/v2/guide/transitions.html

Maybe we can start using this if it is appropriate 😄