Adding MDX Post Snippet Support

[DanialK]

Hi @timlrx

Thank you very much for the awesome project 🙌 ❤️

I recently migrated my old Octopress-based blog to this project and wrote about it here

One feature that Octopress had that was very cool was the idea of snippets (a portion of the original MDX file) which I have hacked together and wrote about it in the Add support for rendering post snippets section and thought I share in case you found it interesting or had any suggestions.

Cheers,

Dan