feat(checkbox): Add public methods for UX state (#632)
feat(checkbox): Add public methods for UX state (#632)

Add the following public methods for controlling `mdc-checkbox` UX state.

* `isChecked(): boolean`
* `isDisabled(): boolean`
* `getValue(): string`
* `setValue(value: string): void`
trimox/angular-mdc-web,trimox/angular-mdc-web