Incorrect visibility calculation with {force: false, offset: nonZero} #138
Description
The scroller can incorrectly decide that an element is already visible when
specifying {force: false, offset: nonZero}. The code checks if targetY is
within the current visible portion of container, but targetY has the
offset applied already.
*------------* | container | | above | *~ ~ ~ ~ ~ ~ * container top | | | visible | | area | | | <-| | | | | | | | | | skips scrolling if elm *~ ~ ~ ~ ~ ~ * | is within this area | *-------* | | | | elm | | | | *-------* | | | | <-| | container | | below | *------------*