[Extension] Add D2 Diagram Rendering Support for Hexo Blogs

[leverimmy]

Recently, I integrated D2 into my Hexo blog and developed a custom plugin for it. Now, you can use the following syntax in your blog posts to render D2 diagrams:

```d2
// Your D2 diagram code here
```

The plugin processes the d2 code block and renders it as a diagram in your blog. This allows seamless integration of D2 diagrams into Hexo without manual setup.

Let me know if you have suggestions for improvement or ideas to enhance the functionality further!