Et2Checkbox: Use normal color even when required

Preveiously check was white, which was hard to see on yellow required background

api/js/etemplate/Et2Checkbox/Et2Checkbox.ts

@@ -39,14 +39,22 @@ export class Et2Checkbox extends Et2InputWidget(SlCheckbox)
 			  }
 
 			  /* Fix positioning */
+
 			  .checkbox {
 				position: relative;
 			  }
 
 			  /* Extend hover highlight to label */
+
 			  .checkbox:not(.checkbox--disabled):hover {
 				color: var(--sl-input-border-color-hover);
 			  }
+
+			  /* Use normal color even when required */
+
+			  :host([required]) .checkbox__control {
+				color: var(--input-text-color);
+			  }
 			`,
 		];
 	}