Add optional dev flag to Nuxt module

[peteromano]

~~In monorepo setup, for example, I'll have only one sandbox "app" (Nuxt calls this a "playground") which will run Storybook in dev mode. If I have many other apps, I don't want to actually run Storybook dev instances per each app (playground pulls stories from all the other apps.)~~

~~However, in production deployments, I do want a static storybook build per each app, so I still want to install Storybook Nuxt on all apps, just not run all apps in dev mode.~~

~~Therefore, it should be optional to auto-install and auto-add the module to an app. The proposal is to make the cli respect a new flag called --module:~~

~~pnpm dlx storybook-nuxt@latest init --module~~

Another solution could be to always install, but use options in Nuxt config for the module, like:

export default defineNuxtConfig({
  modules: [
    '@storybook-vue/nuxt-storybook'
  ],
    
  storybook: {
    // Default to false, as most apps should only run production builds and its "expensive" to run dev servers
    dev: true
  }
})

I think I actually like the second proposal better, and would be extremely simple to make a PR for.

In Nuxt module:

export default defineNuxtModule<ModuleOptions>({
  meta: {
    name: 'storybook-nuxt',
    configKey: 'storybook'
  },
  defaults: {
    dev: false
  },
  async setup (options, nuxt) {

    ....

    if(nuxt.options.dev && options.dev) {
      // Start Storybook dev server
    }
  }
}