Glitching empty area in window mode

[sharpensteel]

In window mode, in page with header, state.displayIndexStart calculated incorrectly, which causes emply space before react-infinite items (see screenshot)

example files to reproduce bug: html + jsx

i created commit that fixesgetScrollTop / setScrollTop so they take into account y-offset of Infinite component on page

screenshot:

[bleshik]

@sharpensteel could you please create a PR so that it gets merged? The lib works well, except this particular bug.

[elnygren]

any chance to get this into the codebase? This fix worked for me. 👍