Code block content is trimmed

[Akryum]

Describe the bug

Writing

```
  A-->B;
  A-->C;
  B-->D;
  C-->D;
```

Should keep the indentation but the content is trimmed so it render like:

```
A-->B;
  A-->C;
  B-->D;
  C-->D;
```

Reproduction

https://stackblitz.com/edit/vite-g3gqwo?file=docs%2Fexample.md

Expected behavior

Doesn't trim the content and render indentation on the first line correctly.

System Info

System:
    OS: Linux 6.4 Fedora Linux 38 (Workstation Edition)
    CPU: (24) x64 AMD Ryzen 9 3900XT 12-Core Processor
    Memory: 27.51 GB / 62.69 GB
    Container: Yes
    Shell: 5.2.15 - /bin/bash
  Binaries:
    Node: 20.6.1 - ~/.local/share/pnpm/node
    Yarn: 1.22.19 - ~/.nvm/versions/node/v16.18.1/bin/yarn
    npm: 9.8.1 - ~/.local/share/pnpm/npm
    pnpm: 8.7.6 - ~/.local/share/pnpm/pnpm
  Browsers:
    Chrome: 117.0.5938.62
  npmPackages:
    vitepress: ^1.0.0-rc.14 => 1.0.0-rc.14

Additional context

No response

Validations

• Check if you're on the latest VitePress version.
• Follow our Code of Conduct
• Read the docs.
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.