Navigator places locator with anchor in the middle of the screen in scroll mode

[chrfalch]

When an EPub navigator is in scroll mode and navigating to a locator with an anchor (ex.: /OEBPS/chapter16.xhtml#endnote-022), the scroll position is calculated to place the target element in the middle of the screen. This can be an issue for footnotes in large indexes because it might not be clear which footnote that was clicked.

See same issue in swift-toolkit here:

readium/swift-toolkit#328