Add a build step to clone the private homepage files.

This is currently used to deploy a PGP WKD (Web Key Directory) for my PGP keys.

docker/server/nginx.conf

@@ -48,6 +48,11 @@ http {
             default_type text/plain;
         }
 
+        location ~ /\.well-known/openpgpkey/[^/]+/hu/ {
+            default_type        "application/octet-stream";
+            add_header          Access-Control-Allow-Origin * always;
+        }
+
         location /.well-known/matrix/server {
           default_type application/json;
           add_header "Access-Control-Allow-Origin" *;