Create new repository for hosting the WindowBuilder website sources (#2)

With the deprecation of PHP within the current year, we need to migrate
HTML or something similar. Hugo is one of the proposed alternative,
which requires its sources to be hosted separately from the actual
website.

Issue:
https://gitlab.eclipse.org/eclipsefdn/helpdesk/-/issues/1934

Hugo template:
https://gitlab.eclipse.org/eclipsefdn/it/webdev/hugo-eclipsefdn-website-boilerplate#how-to-build-my-projects-website-with-jenkins

"Old" website:
https://github.com/eclipse-windowbuilder/windowbuilder-website/

otterdog/eclipse-windowbuilder.jsonnet

@@ -79,5 +79,16 @@ orgs.newOrg('eclipse-windowbuilder') {
         enabled: false,
       },
     },
+    orgs.newRepo('windowbuilder-website-source') {
+      allow_merge_commit: true,
+      allow_update_branch: false,
+      default_branch: "master",
+      delete_branch_on_merge: false,
+      secret_scanning_push_protection: "disabled",
+      web_commit_signoff_required: false,
+      workflows+: {
+        enabled: false,
+      },
+    },
   ],
 }