Check doc block signature to match the specified return type

Signed-off-by: Morris Jobke <hey@morrisjobke.de>

build/.phan/config.php

@@ -144,6 +144,12 @@ return [
 	// to fix in your code base.
 	'quick_mode' => false,
 
+	// If true, check to make sure the return type declared
+	// in the doc-block (if any) matches the return type
+	// declared in the method signature. This process is
+	// slow.
+	'check_docblock_signature_param_type_match' => true,
+
 	// If enabled, check all methods that override a
 	// parent method to make sure its signature is
 	// compatible with the parent's. This check