fix: restore values

changelog.txt

 # Changelog
 
+## [3.1.1] - 2023-03-16
+### Added
+- WPEditorField
+### Deprecated
+- WyswigField
+### Fixed
+
 ## [3.1.0] - 2022-08-30
 ### Added
 - de_DE translations

src/Field/CheckboxField.php

@@ -6,6 +6,9 @@ use WPDesk\Forms\Field;
 
 class CheckboxField extends BasicField {
 
+	const VALUE_TRUE  = 'yes';
+	const VALUE_FALSE = 'no';
+
 	public function get_type(): string {
 		return 'checkbox';
 	}