Add documentation for HelperTrait for IDE auto-completion

docs/book/view-helpers.md

@@ -8,6 +8,30 @@ behaviors for you.
 
 See the section on \[view helpers\](zend.view.helpers) for more information.
 
+> ### IDE auto-completion in templates
+>
+> The `Zend\Form\View\Helper\HelperTrait` trait can be used to provide
+> auto-completion for modern IDEs. It defines the aliases of the view helpers in
+> a DocBlock as `@method` tags.
+>
+> #### Usage
+>
+> In order to allow auto-completion in templates, `$this` variable should be
+> type-hinted via a DocBlock at the top of your template. It is recommended that
+> you always add the `Zend\View\Renderer\PhpRenderer` as the first type, so that
+> the IDE can auto-suggest the default view helpers from `zend-view`. Next,
+> chain the `HelperTrait` from `zend-form` with a pipe symbol (a.k.a. vertical
+> bar) `|`:
+> ```php
+> /**
+> * @var Zend\View\Renderer\PhpRenderer|Zend\Form\View\Helper\HelperTrait $this
+> */
+> ```
+>
+> You may chain as many `HelperTrait` traits as you like, depending on view
+> helpers from which Zend Framework component you are using and would like to
+> provide auto-completion for.
+
 ## Standard Helpers
 
 ## HTML5 Helpers