EnhancedAnchoring plugin:
 - add `getAnchors()` method
 - add `scrollIntoView()` method
 - move some code from the bucket-bar

TextHighlight plugin:
 - get rid of padded scrolling
 - scrollIntoView() no returns a promise

Other:
 - When we click on an annotation card in the sidebar, we need to
   go to the anchor in the document. However, the highlight might
   not exist at this point, so we should look for the Anchor instead.
   So now we call `scrollIntoView()` onthe anchor.
 - The same goes when we click the arrows on the bucket bar
 - Rename `scrollTo` to `scrollIntoView` everywhere.