Henry Chen

Horizontal line disappears when container overflows.

1

Due to the display flex added in [this pr](https://github.com/uiwjs/react-md-editor/commit/aba69a33109c946392781521224a35a13252f696) the horizontal lines shrink and then disappear if the container has too much text. Repro: https://codesandbox.io/s/markdown-editor-for-react-forked-2qq959?file=/index.js Expand the container to have...