Add missing form-control styles import (#1897)

src/components/checkbox/checkbox.component.ts

@@ -8,6 +8,7 @@ import { live } from 'lit/directives/live.js';
 import { property, query, state } from 'lit/decorators.js';
 import { watch } from '../../internal/watch.js';
 import componentStyles from '../../styles/component.styles.js';
+import formControlStyles from '../../styles/form-control.styles.js';
 import ShoelaceElement from '../../internal/shoelace-element.js';
 import SlIcon from '../icon/icon.component.js';
 import styles from './checkbox.styles.js';
@@ -41,7 +42,7 @@ import type { ShoelaceFormControl } from '../../internal/shoelace-element.js';
  * @csspart form-control-help-text - The help text's wrapper.
  */
 export default class SlCheckbox extends ShoelaceElement implements ShoelaceFormControl {
-  static styles: CSSResultGroup = [componentStyles, styles];
+  static styles: CSSResultGroup = [componentStyles, formControlStyles, styles];
   static dependencies = { 'sl-icon': SlIcon };
 
   private readonly formControlController = new FormControlController(this, {