Update documentation

Universalize the default props

components/button/index.en-US.md

@@ -17,7 +17,7 @@ To get a customized button, just set `type`/`shape`/`size`/`loading`/`disabled`.
 | Property | Description | Type | Default |
 | -------- | ----------- | ---- | ------- |
 | disabled | disabled state of button | boolean | `false` |
-| ghost | make background transparent and invert text and border colors, added in 2.7 | boolean | false |
+| ghost | make background transparent and invert text and border colors, added in 2.7 | boolean | `false` |
 | href | redirect url of link button | string | - |
 | htmlType | set the original html `type` of `button`, see: [MDN](https://developer.mozilla.org/en-US/docs/Web/HTML/Element/button#attr-type) | string | `button` |
 | icon | set the icon of button, see: Icon component | string | - |