FlexboxLayoutManager child item margin is wrong when flex-direction is column

[hjhjw1991]

• I have searched existing issues and confirmed this is not a duplicate

Issues and steps to reproduce

Please replace this with steps to reproduce your issue.
parent flex-direction: column
and
only the first child in recyclerview has topMargin.

Expected behavior

Please describe what you expected would happen.
layout should respect child margin correctly

Version of the flexbox library

3.0.0

Link to code

Please link to the code we can use to reproduce this issue.
A complete project we can build/run is preferred, if you can't provide one, please show
us relevant code

I have already figured out what went wrong. see my pull request