feat: support `.svg` file icon in code block titles

[Mini-ghost]

Enables SVG file icon display when using [file.svg] syntax in code blocks.

```html [vue.svg]
<svg xmlns="http://www.w3.org/2000/svg" width="37.07" height="36" viewBox="0 0 256 198">
  <path fill="#41B883" d="m0 0l128 220.8L256 0h-51.2L128 132.48L50.56 0H0Z"></path>
  <path fill="#35495E" d="M50.56 0L128 133.12L204.8 0h-47.36L128 51.2L97.92 0H50.56Z"></path>
</svg>
```

Before

After