Support for Docusaurus v3

[skyfrk]

The plugin is currently not compatible with Docusaurus v3.

Steps to reproduce

1. Create a new docusaurus app npx create-docusaurus@latest my-website classic
2. Install this plugin.
3. Try to render a simple plantuml in Markdown:

```plantuml Your title
class SimplePlantUMLPlugin {
    + transform(syntaxTree: AST): AST
}
```

4. Get an error

Notes

Its probably an issue caused by the migration to MDX v3: https://docusaurus.io/docs/migration/v3#upgrading-mdx

[mstroppel]

Shown error is:

Error: MDX compilation failed for file "C:\data\github\remark-local-plantuml-docusaurus\docs\simple.md"
Cause: Cannot handle unknown node `raw`
Details:
Error: Cannot handle unknown node `raw`

[mstroppel]

@ksandin already created a workaround for something similar:
shikijs/twoslash#125 (comment)

[mstroppel]

I added a workaround for docusaurus v3 in #9
See the main page.

[mstroppel]

@ksandin already created a workaround for something similar: shikijs/twoslash#125 (comment)

This fix is used here https://github.com/mstroppel/remark-local-plantuml-docusaurus/tree/fix/hacky-docusaurus-v3-fix
But I would not recommend it, since it is pretty hacky.

[mstroppel]

Workaround was seen here https://github.com/excaliburjs/Excalibur/pull/2793/files#diff-6165458b00f7d0251872e75af62bd54496e809f8793639ccd4d5b7461b017806
Thanks to @kamranayub