Publish the documentation on GitHub pages

[mnonnenmacher]

Publish the documentation of the ORT Server on GitHub pages. As we already use Docusaurus for ORT itself and for the guidance repo that would be my preferred tool here as well.

The most interesting alternative for me would be mkdocs-material which is also very popular. However, I would still prefer Docusaurus for the following reasons:

• We are already using it for ORT and the Apoapsis guidance documentation. This gives the documentation a consistent appearance and we are already familiar with the tool.
• There is a plugin for OpenAPI which we could use to integrate the OpenAPI specs (mkdocs has this as well).
• There is a plugin for Dokka which we could use to integrate the code API docs.
• As we have React developers among the committers, we could later create a nice landing page directly in Docusaurus, AFAIK this is not possible with mkdocs-material.

[mnonnenmacher]

Related to #256.

[sschuberth]

Also somewhat related is the logo discussion over here.

[mnonnenmacher]

The website is now published at https://eclipse-apoapsis.github.io/ort-server/ but I want to add some actual documentation content before closing this ticket.