message: docs(PasswordInput): adjust demo
diff: @@ -19,18 +19,14 @@ Vue.use(NumberKeyboard);
  ### Basic Usage
  ```html
  -<!-- PasswordInput -->
  <van-password-input
  :value="value"
  - info="Some tips"
  :focused="showKeyboard"
  @focus="showKeyboard = true"
  />
  -<!-- NumberKeyboard -->
  <van-number-keyboard
  + v-model="value"
  :show="showKeyboard"
  - @input="onInput"
  - @delete="onDelete"
  @blur="showKeyboard = false"
  />
  ```
  @@ -43,30 +39,32 @@ export default {
  showKeyboard: true,
  };
  },
  - methods: {
  - onInput(key) {
  - this.value = (this.value + key).slice(0, 6);
  - },
  - onDelete() {
  - this.value = this.value.slice(0, this.value.length - 1);
  - },
  - },
  };
  ```
  -### Custom length
  +### Custom Length
  ```html
  <van-password-input
  :value="value"
  - :length="4"
  :gutter="15"
  :focused="showKeyboard"
  @focus="showKeyboard = true"
  />
  ```
  -### Without mask
  +### Add Gutter
  +
  +```html
  +<van-password-input
  + :value="value"
  + :gutter="10"
  + :focused="showKeyboard"
  + @focus="showKeyboard = true"
  +/>
  +```
  +
  +### Without Mask
  ```html
  <van-password-input
  @@ -79,22 +77,19 @@ export default {
  ### Hint Error
  -Use `error-info` prop to set error message. For example, a password error is prompted when entering 6 bits.
  +Use `info` to set info message, use `error-info` prop to set error message.
  ```html
  -<!-- PasswordInput -->
  <van-password-input
  :value="value"
  + info="Some tips"
  :error-info="errorInfo"
  :focused="showKeyboard"
  @focus="showKeyboard = true"
  />
  -
  -<!-- NumberKeyboard -->
  <van-number-keyboard
  + v-model="value"
  :show="showKeyboard"
  - @input="onInput"
  - @delete="onDelete"
  @blur="showKeyboard = false"
  />
  ```
  @@ -104,22 +99,18 @@ export default {
  data() {
  return {
  value: '123',
  - showKeyboard: true,
  errorInfo: '',
  + showKeyboard: true,
  };
  },
  - methods: {
  - onInput(key) {
  - this.value = (this.value + key).slice(0, 6);
  - if (this.value.length === 6) {
  + watch: {
  + value(value) {
  + if (value.length === 6 && value !== '123456') {
  this.errorInfo = 'Password Mistake';
  } else {
  this.errorInfo = '';
  }
  },
  - onDelete() {
  - this.value = this.value.slice(0, this.value.length - 1);
  - },
  },
  };
  ```
  