Repository: storybook
Issue: [Bug]: public subfolders are not served from URL root when setting it on staticDirs array
Labels: bug,nextjs,sev:S3

### Describe the bug

By logic, for the following `staticDirs` all its subfolders should be set up as URLs of `/`: `  staticDirs: ["../public"],`.
So, it should be `/` for root (`public`) and `/fonts` for subfolder(`public/fonts`).

Well, any subfolder of `public` becomes `/public/*`.

It is especially important when working with **next/fonts** since **Storybook** is looking to import the fonts from `/fonts`, making it unable to load fonts properly, see this issue: https://github.com/storybookjs/storybook/issues/19711#issuecomment-1942958750.

As a workaround we use:
```ts
  staticDirs: [
    {
      from: "../public",
      to: "public",
    },
    { from: "../public/fonts", to: "fonts" },
  ],
```
Altogether with our decorator, it works. But this solution conflicts with `msw-storybook-addon` which looks for the worker file on the root URL.

### To Reproduce

1. Create a new NextJS project.
2. Set up the addon.
3. Setup the `staticDirs`:
```ts
  /*
  TODO: https://github.com/storybookjs/storybook/issues/19711#issuecomment-1942958750
  staticDirs: [
    {
      from: "../public",
      to: "public",
    },
    { from: "../public/fonts", to: "fonts" },
  ],
  TODO: https://github.com/mswjs/msw-storybook-addon/issues/136
  */
  staticDirs: ["../public"],
```
4. Create your decorator for importing fonts on the **storybooks**:
```ts
export const FontDecorator = (Story) => (
  <main className={clsx(fonts.notoSerif.variable, fonts.trt.variable)}>
    <Story />
  </main>
);
```
```ts
const preview: Preview = {
  decorators: [
    FontDecorator,
    IntlDecorator,
  ],
```
5. Run Storybook.
6. Check the fonts are not being loaded:
![image](https://github.com/storybookjs/storybook/assets/5034215/a2b367ef-f1a5-4b8f-9a87-0b3c04ad03b6)
7. Check the link `http://localhost:6006/public/fonts/TRT-Bold.woff2`, remove `public/` from that URL, and you will get the font loaded.

### System

```bash
Storybook Environment Info:

  System:
    OS: Linux 6.1 Manjaro Linux
    CPU: (16) x64 AMD Ryzen 9 5900HX with Radeon Graphics
    Shell: 5.2.26 - /bin/bash
  Binaries:
    Node: 20.11.0 - ~/.nvm/versions/node/v20.11.0/bin/node
    Yarn: 1.22.21 - /usr/bin/yarn
    npm: 10.2.4 - ~/.nvm/versions/node/v20.11.0/bin/npm
    pnpm: 8.15.4 - /usr/bin/pnpm <----- active
  npmPackages:
    @storybook/addon-a11y: 8.0.0-beta.6 => 8.0.0-beta.6 
    @storybook/addon-essentials: 8.0.0-beta.6 => 8.0.0-beta.6 
    @storybook/addon-interactions: 8.0.0-beta.6 => 8.0.0-beta.6 
    @storybook/addon-links: 8.0.0-beta.6 => 8.0.0-beta.6 
    @storybook/addon-onboarding: 8.0.0-beta.6 => 8.0.0-beta.6 
    @storybook/addon-storysource: 8.0.0-beta.6 => 8.0.0-beta.6 
    @storybook/addon-themes: 8.0.0-beta.6 => 8.0.0-beta.6 
    @storybook/blocks: 8.0.0-beta.6 => 8.0.0-beta.6 
    @storybook/nextjs: 8.0.0-beta.6 => 8.0.0-beta.6 
    @storybook/react: 8.0.0-beta.6 => 8.0.0-beta.6 
    @storybook/test: 8.0.0-beta.6 => 8.0.0-beta.6 
    @storybook/theming: 8.0.0-beta.6 => 8.0.0-beta.6 
    eslint-plugin-storybook: 0.8.0 => 0.8.0 
    msw-storybook-addon: 2.0.0-beta.1 => 2.0.0-beta.1 
    storybook: 8.0.0-beta.6 => 8.0.0-beta.6 
    storybook-addon-rtl: 1.0.0 => 1.0.0
```


### Additional context

It is related to [this issue](https://github.com/mswjs/msw-storybook-addon/issues/136#issuecomment-1969966708) and it is especially important we are working with **next/fonts**, [see here](https://github.com/storybookjs/storybook/issues/19711#issuecomment-1942958750).