update documentation

src/server/backend/db/db.js

@@ -173,4 +173,7 @@ module.exports.deleteJSONDataSimple = ( db, identifier ) => {
             }
         } );
     } );
-};
+};
+
+// TODO: Build garbage collector for DB (parse DB every so often (get from settings) 
+// and delete all items where timestamp is older than a certain amount of time (get from settings))