fix(alert): use interpolation for type attribute

Closes #1460

BREAKING CHANGE: Use interpolation for type attribute.

  Before:

  ```html
  <alert type="'info'" ...></alert >
  ```
  or
  ```html
  <alert type="alert.type" ...></alert >
  ```

  After:

  ```html
  <alert type="info" ...></alert >
  ```
  or
  ```html
  <alert type="{{alert.type}}" ...></alert >
  ```