Unify how --format is handle by commands

Author: fabpot

Command/LintCommand.php

@@ -72,6 +72,9 @@ protected function configure(): void
 Or of a whole directory:
 
   <info>php %command.full_name% dirname</info>
+
+The <info>--format</info> option specifies the format of the command output:
+
   <info>php %command.full_name% dirname --format=json</info>
 
 You can also exclude one or more specific files:
@@ -266,6 +269,7 @@ public function complete(CompletionInput $input, CompletionSuggestions $suggesti
         }
     }
 
+    /** @return string[] */
     private function getAvailableFormatOptions(): array
     {
         return ['txt', 'json', 'github'];