[storybook-addon-a11y] Merge a11y.config.rules on story and global levels

[yknyshich]

Is your feature request related to a problem? Please describe.

Hello! I've faced the issue similar to mswjs/msw-storybook-addon#43
For example, if there are rules defined both on global level

// .storybook/preview.js

const paramters = {
  a11y: {
    config: {
      rules: [
        {
            enabled: false,
            id: 'frame-tested',
        },
      ],
    },
  },
}

and story level

// component.stories.tsx

export const Inaccessible = () => (
  <button style={{ backgroundColor: 'red', color: 'darkRed' }}>Inaccessible button</button>
);
Inaccessible.parameters = {
  a11y: {
    config: {
      rules: [{ id: 'color-contrast', enabled: false }],
    },
  },
};

then global ones will be overridden in resulting config

// __STORYBOOK_PREVIEW__.currentRender.story.parameters

{
  a11y: {
    config: {
      rules: [{ id: 'color-contrast', enabled: false }],
    },
  },
}

This is correct behaviour based on parameter-inheritance

ℹ️ Parameters are merged, so objects are deep-merged, but arrays and other properties are overwritten.

But it is really inconvenient in case we want to turn off a couple of rules for all stories and then ignore one more in a single story.

Describe the solution you'd like

It would help a lot if config.rules could accept not only array

// .storybook/preview.js

const paramters = {
  a11y: {
    config: {
      rules: [
        {
          id: 'color-contrast',
          enabled: false,
        }, 
      ],
    },
  },
}

but also object

// .storybook/preview.js

const paramters = {
  a11y: {
    config: {
      rules: { 
        'color-contrast': { enabled: false } 
        },
    },
  },
}

Then rules will be merged

Describe alternatives you've considered

No response

Are you able to assist to bring the feature to reality?

yes, I can

Additional context

No response