Fix return type of *DocBlockHint() methods - Close #49

Author: sandrokeil

src/Builder/ClassMethodBuilder.php

@@ -241,7 +241,7 @@ public function setDocBlockComment(?string $docBlockComment): self
         return $this;
     }
 
-    public function getReturnTypeDocBlockHint(): string
+    public function getReturnTypeDocBlockHint(): ?string
     {
         return $this->returnTypeDocBlockHint;
     }

src/Builder/ClassPropertyBuilder.php

@@ -179,7 +179,7 @@ public function setDocBlockComment(?string $docBlockComment): self
         return $this;
     }
 
-    public function getTypeDocBlockHint(): string
+    public function getTypeDocBlockHint(): ?string
     {
         return $this->typeDocBlockHint;
     }

src/Builder/ParameterBuilder.php

@@ -152,7 +152,7 @@ public function getName(): string
         return $this->name;
     }
 
-    public function getTypeDocBlockHint(): string
+    public function getTypeDocBlockHint(): ?string
     {
         return $this->typeDocBlockHint;
     }