[Feature request] Option to disable isAtBottom

[hrishikesh-k]

Hi!

Thanks for the great library, works amazingly.

I do have a small request though and would be very thankful if it's taken into consideration and implemented. It's a personal opinion, so others might feel differently.

According to me, the isAtBottom() part should be a configurable option. This is because, in its current implementation, it directly skips over a lot of list items. For example, I'm working on a documentation website and in that, I've a lot of headings with small descriptions. Thus, till the extreme end the headings are correctly highlighted, however as soon as document reaches the end, the list items skip over many headings and jumps to the last one. To me, this feels like a glitch rather than a feature.

For example, in this image, the highlighted item before isAtBottom() is form:

But as soon as you scroll a pixel down to reach the end, it jumps to title skipping the 3 others in between. I'd rather prefer if it doesn't do that and highlight the one according to the top offset like it does for other headings.

I understand that others might think differently and thus, adding this as a configuration option makes more sense.