feat(checkbox): add required prop (#30157)

Issue number: resolves internal

---------

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## What is the current behavior?
- Currently, the screen reader do not announce the component as required
when `required={true}`.

## What is the new behavior?
- Added a new `required` prop to be used for accessibility purposes that
adds the `required` attribute to checkbox's inner native input.

## Does this introduce a breaking change?

- [ ] Yes
- [x] No

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core/src/components/checkbox/checkbox.tsx

@@ -98,6 +98,13 @@ export class Checkbox implements ComponentInterface {
    */
   @Prop() alignment?: 'start' | 'center';
 
+  /**
+   * If true, screen readers will announce it as a required field. This property
+   * works only for accessibility purposes, it will not prevent the form from
+   * submitting if the value is invalid.
+   */
+  @Prop() required = false;
+
   /**
    * Emitted when the checked property has changed as a result of a user action such as a click.
    *
@@ -182,6 +189,7 @@ export class Checkbox implements ComponentInterface {
       name,
       value,
       alignment,
+      required,
     } = this;
     const mode = getIonMode(this);
     const path = getSVGPath(mode, indeterminate);
@@ -218,6 +226,7 @@ export class Checkbox implements ComponentInterface {
             onFocus={() => this.onFocus()}
             onBlur={() => this.onBlur()}
             ref={(focusEl) => (this.focusEl = focusEl)}
+            required={required}
             {...inheritedAttributes}
           />
           <div