Added style class definitions to *Style.d.ts

components/lib/checkbox/style/CheckboxStyle.d.ts

@@ -1,3 +1,19 @@
+/**
+ *
+ * Checkbox is an extension to standard checkbox element with theming.
+ *
+ * [Live Demo](https://www.primevue.org/checkbox/)
+ *
+ * @module checkboxstyle
+ *
+ */
 import { BaseStyle } from '../../base/style';
 
+export enum CheckboxClasses {
+    root = 'p-checkbox',
+    box = 'p-checkbox-box',
+    input = 'p-checkbox-input',
+    icon = 'p-checkbox-icon'
+}
+
 export interface CheckboxStyle extends BaseStyle {}