message: fix inline overlay positioning
diff: @@ -105,7 +105,9 @@ export const Overlay: React.FunctionComponent<{
  }
  const InlineOverlayWrapper = styled.div((props: ThemeProps<EditorTheming>) => ({
  - position: 'fixed',
  + position: 'absolute',
  + top: '-10000px',
  + left: '-10000px',
  opacity: 0,
  transition: 'opacity 0.5s',
  backgroundColor: props.theme.backgroundColor,
  @@ -148,11 +150,14 @@ export const InlineOverlay: React.FunctionComponent<{
  const range = native.getRangeAt(0)
  const rect = range.getBoundingClientRect()
  if (rect.height === 0) return
  + // menu is set to display:none, shouldn't ever happen
  + if (!menu.offsetParent) return
  + const parentRect = menu.offsetParent.getBoundingClientRect()
  menu.style.opacity = '1'
  - menu.style.top = `${rect.bottom + window.pageYOffset + 3}px`
  + menu.style.top = `${rect.bottom - parentRect.top + 3}px`
  menu.style.left = `${Math.max(
  - rect.left + window.pageXOffset - menu.offsetWidth / 2 + rect.width / 2,
  + rect.left - parentRect.left - menu.offsetWidth / 2 + rect.width / 2,
  0
  )}px`
  }, [overlay])
  