Bug: Heading permalink extension not being enabled when compiling the body for documentation pages

[caendesilva]

This is because the extension gets enabled automatically when the source model is set to DocumentationPage, however, the StaticPageBuilder.php never supplies that parameter to the Markdown converter.

Desired behavior is fixed by changing

 'markdown' => MarkdownConverter::parse($this->page->body),

To

'markdown' => (new MarkdownConverterService($this->page->body, DocumentationPage::class))->parse(),