Add a way to add description to virtual modules

Clear and concise description of the problem

I think it would be helpful for users if there's a description for each virtual modules. For example:

• rolldown/runtime.js: rolldown's utilty functions that are used in the bundle
• vite/modulepreload-polyfill.js: Vite's modulepreload polyfill. See https://vite.dev/config/build-options#build-modulepreload
• ./src/App.vue?vue&type=script&setup=true&lang.ts: <script> block of ./src/App.vue

Suggested solution

Recommend plugins to add meta.devtools.description values in load hook.

const p = {
  name: 'foo',
  load(id) {
    return { code: content, meta: { devtools: { description: 'Vite's modulepreload polyfill. See https://vite.dev/config/build-options#build-modulepreload' } } }
  }
}

and make devtools will read that information.

Alternative

Add the metadata on plugin object:

const p = {
  name: 'foo',
  meta: {
    devtools: {
      virtualmodulesDescription: {
        'vite/modulepreload-polyfill.js': 'Vite's modulepreload polyfill. See https://vite.dev/config/build-options#build-modulepreload',
      }
    }
  }
}

This does not allow setting the description for dynamic virtual modules.

Additional context

No response

Validations

• Follow our Code of Conduct
• Read the Contributing Guide.
• Check that there isn't already an issue that request the same feature to avoid creating a duplicate.

Start by tracing the plugin load hook and the devtools handling of module metadata, focusing on the proposed meta.devtools.description value and the virtualmodulesDescription alternative. The work is done when virtual modules can expose descriptions, including dynamically created modules, and devtools display those descriptions.