[TypeDeclaration] Add VarTypeDeclarationRector

```diff
 class SomeClass
 {
+    /**
+     * @var Dispatcher
+     */
     private $dispatcher;

     public function __construct(Dispatcher $dispatcher)
     {
         $this->dispatcher = $dispatcher;
     }
 }
```

Similar to:

- `ReturnTypeDeclarationRector`
- `ParamTypeDeclarationRector`

Inspire at:

- `CompleteDynamicPropertiesRector`