```js
// .storybook/my-addon/preset.js

export function config(entry = []) {
  return [...entry, require.resolve('./defaultParameters')];
}

export function managerEntries(entries) {
  return [...entries, require.resolve('./register')];
}

export const parameters = {
  backgrounds: {
    values: [
      { name: 'light', value: '#F8F8F8' },
      { name: 'dark', value: '#333333' },
    ],
  },
};
```