Newlines should be disregarded in Markdown

### Describe the bug

When writing docs in a Story, newlines should be regarded simply as spaces (standard Markdown behavior).

Example:
```html

# DotMenu

A simple menu component that displays a list of items in a dropdown menu. You
can supply
an
array
of... why is this happening?

```

renders:

But if you edit a README.md on GitHub and paste Markdown with newlines, it renders as a single sentence. Writing in a single line to achieve soft wrap is not practical:

### Reproduction

Not necessary.

### System Info

```shell
System:
OS: macOS 12.6.2
CPU: (8) arm64 Apple M1
Memory: 89.48 MB / 16.00 GB
Shell: 5.8.1 - /bin/zsh
Binaries:
Node: 18.12.1 - ~/Library/Caches/fnm_multishells/7647_1676908209116/bin/node
Yarn: 1.22.19 - ~/Library/Caches/fnm_multishells/7647_1676908209116/bin/yarn
npm: 8.19.2 - ~/Library/Caches/fnm_multishells/7647_1676908209116/bin/npm
Browsers:
Chrome: 110.0.5481.100
Firefox: 108.0.2
Safari: 16.2
npmPackages:
@histoire/plugin-vue: ^0.15.8 => 0.15.8
@vitejs/plugin-vue: ^4.0.0 => 4.0.0
histoire: ^0.15.8 => 0.15.8
vite: ^4.1.2 => 4.1.1
```

### Used Package Manager

pnpm

### Validations

- [X] Follow our [Code of Conduct](https://github.com/histoire-dev/histoire/blob/main/CODE_OF_CONDUCT.md)
- [X] Read the [Contributing Guidelines](https://github.com/histoire-dev/histoire/blob/main/CONTRIBUTING.md).
- [X] Read the [docs](https://histoire.dev/guide/).
- [X] Check that there isn't [already an issue](https://github.com/histoire-dev/histoire/issues) that reports the same bug to avoid creating a duplicate.
- [X] Check that this is a concrete bug. For Q&A open a [GitHub Discussion](https://github.com/histoire-dev/histoire/discussions).
- [X] The provided reproduction is a [minimal reproducible example](https://stackoverflow.com/help/minimal-reproducible-example) of the bug.

No source files or tests are named in the issue. Start by locating the Markdown rendering path used for docs in a Story, then reproduce the example and add coverage showing that ordinary newlines render as spaces while intentional paragraph breaks remain distinct.

Written by the indexing model from the issue text.