message: docs(readme): add classname prop
diff: @@ -74,6 +74,7 @@ const BasicFlow = () => (
  - `nodeTypes`: object with [node types](#node-types--custom-nodes)
  - `edgeTypes`: object with [edge types](#edge-types--custom-edges)
  - `style`: css style passed to the wrapper
  +- `className`: additional class name
  - `connectionLineType`: connection line type = `straight` or `bezier`
  - `connectionLineStyle`: connection style as svg attributes
  - `deleteKeyCode`: default: `8` (delete)
  