Add a new setting to configure the URL of the Kroki server

[rasmusmk]

Possibility to send kroki generation to local server/port
and maybe a selection to use cloud if no local response

[frankbenoit]

I find this really important for use at work.
It is not acceptable by the company that internals go to a public server.
On the other hand, asciidoc is important for technical documentation.
To see e.g. plantuml in the preview, I use then AsciidocFx, mainly for this use case only.
The alternative, setting :kroki-server-url: in each document seems also not a good approach, nor does it work for me.
Please support this as a setting in the asciidoc vs code plugin.

[ggrossetie]

Kroki is disabled by default and you can configure the server using the kroki-server-url attribute from the extension settings:

[ggrossetie]

With the upcoming support of the Asciidoctor Config File, you will also be able to set the kroki-server-url attribute in an .asciidoctorconfig file. See: #636

[ggrossetie]

I'm willing to provide a new setting to set the Kroki URL similar to what the Intellij IDEA plugin does:

[ggrossetie]

and maybe a selection to use cloud if no local response

I don't think that's a good idea for privacy reasons. As mentioned by @frankbenoit, it might not be acceptable to send diagrams to a public server.

[nolange]

I would be welcoming this setting aswell, it should take preference over a ASCII Doctor Config file for the preview.