Position problem occurred after portal being dropped.

[ETRick]

'position: fixed' will perform like 'position: absoulate' when beding child of node with 'tranform'. This is what I met when update react-contexify to 5.0.0：When I modified react-contexify element' style left, top to '0', it only stiky to the left top of it's parent:

Here's discussion on stackoverflow: https://stackoverflow.com/questions/2637058/positions-fixed-doesnt-work-when-using-webkit-transform

Here's my example: https://codesandbox.io/s/react-contexify-menu-position-error-forked-te0ug

https://github.com/fkhadra/react-contexify/blob/5a5a1b50e7056debb3b167985efbc33f422bb5b0/src/components/Menu.tsx#L315