Kept the prototype out of search engines in the Website service.

Services/Website/Sources/Library/Public/Extensions/AbsoluteConfigKey+Constants.swift

@@ -82,6 +82,11 @@ extension AbsoluteConfigKey {
         /// The absolute configuration key for the directory the static files are served from.
         public static let staticFiles: AbsoluteConfigKey = .init(.Path.staticFiles)
     }
+    /// A namespace for the site configuration keys, as absolute keys.
+    public enum Site {
+        /// The absolute configuration key for letting search engines index the site.
+        public static let indexable: AbsoluteConfigKey = .init(.Site.indexable)
+    }
     /// A namespace for the security headers configuration keys, as absolute keys.
     public enum Security {
         /// The absolute configuration key for the `Content-Security-Policy` header value.