Fix bug missing setting setOmitted(true) in Button.php

If form is submitted with standard SubmitButton and in the form is another button Button, the attribute name + value appears in $values of the form. This is undesirable behaviour and my proposal fixes this bug.

src/Forms/Controls/Button.php

@@ -23,6 +23,7 @@ public function __construct(string|Stringable|null $caption = null)
 		parent::__construct($caption);
 		$this->control->type = 'button';
 		$this->setOption('type', 'button');
+		$this->setOmitted(true);
 	}