Support view attribute for Structurizr docs rendered with Kroki

[timw]

Why the new feature should be added

Related to asciidoctor/asciidoctor-kroki#418, but asciidoctor-intellij-plugin seems to have it's own Kroki processor.

Using asciidoctor-intellij-pluginto render Asciidoc with Structurizr diagrams containing multiple views, only the last view defined in the Structurizr diagram is rendered in the preview when using Kroki to render diagrams.

With a large Structurizr workspace (which might commonly be managed in an external file to the Asciidoc) there will be many views, so these aren't rendered correctly in the preview.

How the new feature should work

Asciidoctor-diagram defines the view attribute 1 for specifying the view to render.
Kroki defines the view-key option 2 to specify the view to render for Structurizr inputs.

It would be great if the preview renderer could map the standard view attribute on the diagram block to the Kroki view-key option so these diagrams are rendered correctly in preview.