Provide request headers in response function

[chaptergy]

Sometimes the mock response should depend on a header send with the request, for example if the Accept or Accept-Language header was set. This would make request handlers like this possible:

story.parameters = {
    mockData: [
        url: 'https://jsonplaceholder.typicode.com/todos/1',
        method: 'GET',
        status: 200,
        response: (request) => {
            const { headers } = request;

            if (headers.get('Accept-Language') === 'fr-FR') {
                return {
                    data: 'Données en français',
                };
            }
            return { data: 'Default data' };
        },
    ],
};