Option to only scroll up and option to set an offset to the final position

We need two features:

Scroll one item of a long list to the top of the browser window - and only to the top of it. I called the option ``.alignWithTop`` with respect to the native ``.scrollIntoView()`` and its alignWithTop-argument. The type of ``.alignWithTop`` is boolean.

The second feature is an option to set some offset to the position to scroll to. I called the option ``.offset``. The type of ``.offset`` is number || integer.

This PR implements both.