message: docs: add vid to observer reference docs
diff: @@ -318,6 +318,7 @@ Below is the reference of the ValidationObserver public API.
  | tag | `string` | `span` | The default tag to [render](#rendering). |
  | slim | `boolean` | `false` | If true, it will make the observer [renderless](#renderless), only rendering the HTML inside its slot. |
  | disabled | `boolean` | `false` | If true, the observer will be ignored when `validate` is called by a parent observer. |
  +| vid | `string` | random string | if provided it will be used as the observer's id when being registered as a child of a parent observer. |
  ### Methods
  