Diagrams not rendered in Jekyll posts

[felixvanoost]

When running jekyll-kroki on a site that contains Jekyll posts, the diagram descriptions in the post Markdown files are not rendered as images:

Diagram description:

```plantuml
skinparam dpi 125
skinparam packageTitleAlignment left

rectangle "Main" {
  (main.view)
  (singleton)
}
rectangle "Base" {
  (base.component)
  (component)
  (model)
}
rectangle "<b>main.ts</b>" as main_ts

(component) ..> (base.component)
main_ts ==> (main.view)
(main.view) --> (component)
(main.view) ...> (singleton)
(singleton) ---> (model)
```

Rendered HTML:

<pre><code class="language-plantuml">skinparam ranksep 20
skinparam dpi 125
skinparam packageTitleAlignment left

rectangle "Main" {
  (main.view)
  (singleton)
}
rectangle "Base" {
  (base.component)
  (component)
  (model)
}
rectangle "&lt;b&gt;main.ts&lt;/b&gt;" as main_ts

(component) ..&gt; (base.component)
main_ts ==&gt; (main.view)
(main.view) --&gt; (component)
(main.view) ...&gt; (singleton)
(singleton) ---&gt; (model)
</code></pre>

jekyll-kroki should render diagrams in all Jekyll document types.