PluginData.preferences() added.

src/main.vala

@@ -38,6 +38,14 @@ namespace LAview.Core.Plugins {
 			return _("Data Example");
 		}
 
+		/**
+		 * Open Preferences.
+		 */
+		public override void preferences () {
+			// TODO: Open Preferences window.
+			stdout.puts("Data Example preferences () called.\n");
+		}
+
 		/**
 		 * transfer string data
 		 */