Sets the open attribute on the element, if the expression inside ngOpen is truthy.
A special directive is necessary because we cannot use interpolation inside the open
attribute. See the interpolation guide for more info.
<DETAILS
  ng-open="expression">
...
</DETAILS>
      | Param | Type | Details | 
|---|---|---|
| ngOpen | expression | 
         If the expression is truthy, then special attribute "open" will be set on the element  | 
    
<label>Check me check multiple: <input type="checkbox" ng-model="open"></label><br/>
<details id="details" ng-open="open">
   <summary>Show/Hide me</summary>
</details>