chore: add postcss-lit comment to disable Stylelint warning (#9858)

Author: web-padawan

packages/field-base/src/styles/checkable-base-styles.js

@@ -6,6 +6,7 @@
 import '@vaadin/component-base/src/style-props.js';
 import { css, unsafeCSS } from 'lit';
 
+// postcss-lit-disable-next-line
 export const checkable = (part, propName = part) => css`
   :host {
     align-items: center;