message: fixed Button component property type
diff: @@ -24,7 +24,7 @@ export interface ButtonProps extends HasStyleObject, HasChildren, HasClassName {
  stretched?: boolean,
  before?: React.ReactNode,
  after?: React.ReactNode,
  - component?: string | React.ComponentType | React.FunctionComponent
  + component?: string | React.ComponentType
  }
  const mapOldLevel = level => {
  