🎉 Rule #300 - [CodeQuality] Add CompleteDynamicPropertiesRector

[TomasVotruba]

Closes #1476

In PHP 7.3-

 class SomeClass
 {
+    /**
+     * @var string
+     */
+    public $outputFormat;

     public function run()
     {
         $this->outputFormat = 'name';
     }
 }

In PHP 7.4+

 class SomeClass
 {
+    public string $outputFormat;

     public function run()
     {
         $this->outputFormat = 'name';
     }
 }