message: update mergebox demo
diff: -import {MergeStatus, PointerBox, FlexContainer} from '../../src'
  -import {MergeDetail} from '../doc-components/MergeDetail'
  -import MergeActions from '../doc-components/MergeActions'
  -
  -
  -### MergeBox
  +# MergeBox
  ```.jsx
  <FlexContainer alignItems="start">
  