create contextmanager and refactor docgeneratorTemplateType

src/Bundle/ChillDocGeneratorBundle/Context/DocGeneratorContextInterface.php

@@ -16,6 +16,11 @@ namespace Chill\DocGeneratorBundle\Context;
  */
 interface DocGeneratorContextInterface
 {
+
+    public static function getKey(): string;
+
+    public function getName(): string;
+
     /**
      * Get the data that will be injected to the generated document.
      *