Add support for Djot. It uses official djot.js to parse Djot files.

pnpm add hexo-renderer-djot

Djot do not support raw HTML in its source file, so the renderer will disable nunjucks since they are not compatible.

If you want to add any HTML in your Djot file, you can use Raw block in Djot.

``` =html
<div>some raw html</div>
```

Since hexo version 6.1.0, If trying to use both markdown and djot at the same time, post_asset_folder must be set to false. Currently hexo depends on ext of new_post_name to determine whether a file in source folder is renderable or not if post_asset_folder is set to true to prevent render of asset files.

Its false by default, so you don't need to worry if you haven't set it before.

Currently only support setting katex output format.

djot:
    math:
        output: "html" | "mathml"