Compatibility with snippets

[watermarkhu]

Is your feature request related to a problem? Please describe.
To keep the Markdown file as clean as possible. It would be great if mkdocs-puml would be compatible with snippets.

Using snippets, the PlantUML diagrams can remain as separate files.

mkdocs.yml
docs
|-- diagram.puml
|-- index.md

The diagram would be generated with the following syntax in index.md.

```puml
--8<-- "docs/diagram.puml
```

Currently, the mkdocs-puml plugin is triggered before any markdown extensions are evaluated. Resulting in the following:

[watermarkhu]

Alternatively, I see that mkdocs-d2-plugins implements import tags https://landmaj.github.io/mkdocs-d2-plugin/guide/configuration/#image-tags

[MikhailKravets]

Hi @watermarkhu! Thanks for this suggestion and the link above 🔥 This is a great idea to add the support for snippets to the plugin. I'll take a look to that of course. I can't promise it will be right away but in the nearest future for sure.