[Document] add form components english document (#199)

* [Document] add english document of Checkbox

* [Document] add english document of Field

* [Document] add english document of NumberKeyboard

* [bugfix] NumberKeyboard should not dispaly title when title is empty

* [Document] add english document of PasswordInput

* [Document] add english document of Radio

* [document] add english document of Switch

* [bugfix] remove redundent styles in english document

* [Document] fix details

* fix Switch test cases

docs/examples-docs/zh-CN/number-keyboard.md

@@ -84,7 +84,7 @@ export default {
 | 参数 | 说明 | 类型 | 默认值 | 可选值 |
 |-----------|-----------|-----------|-------------|-------------|
 | show | 是否显示键盘 | `Boolean`  | - | - |
-| title | 键盘标题 | `String` | `安全输入键盘` | - |
+| title | 键盘标题 | `String` | - | - |
 | extraKey | 左下角按键内容 | `String`  | `''` | - |
 | zIndex | 键盘 z-index | `Number`  | `100` | - |
 | transition | 是否开启过场动画 | `Boolean`  | `true` | - |
@@ -92,7 +92,7 @@ export default {
 
 ### Event
 
-| 事件名       | 说明      | 参数       |
+| 事件名 | 说明 | 参数 |
 |-----------|-----------|-----------|
 | input | 点击按键时触发 | key: 按键内容 |
 | delete | 点击删除键时触发 | - |